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Markdown
688 lines
25 KiB
Markdown
---
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slug: /en/sql-reference/functions/uuid-functions
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sidebar_position: 205
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sidebar_label: UUIDs
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---
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# Functions for Working with UUIDs
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## generateUUIDv4
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Generates a [version 4](https://tools.ietf.org/html/rfc4122#section-4.4) [UUID](../data-types/uuid.md).
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**Syntax**
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``` sql
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generateUUIDv4([expr])
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```
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**Arguments**
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- `expr` — An arbitrary [expression](../syntax.md#syntax-expressions) used to bypass [common subexpression elimination](../functions/index.md#common-subexpression-elimination) if the function is called multiple times in a query. The value of the expression has no effect on the returned UUID. Optional.
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**Returned value**
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A value of type UUIDv4.
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**Example**
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First, create a table with a column of type UUID, then insert a generated UUIDv4 into the table.
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``` sql
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CREATE TABLE tab (uuid UUID) ENGINE = Memory;
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INSERT INTO tab SELECT generateUUIDv4();
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SELECT * FROM tab;
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```
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Result:
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```response
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┌─────────────────────────────────uuid─┐
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│ f4bf890f-f9dc-4332-ad5c-0c18e73f28e9 │
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└──────────────────────────────────────┘
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```
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**Example with multiple UUIDs generated per row**
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```sql
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SELECT generateUUIDv4(1), generateUUIDv4(2);
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┌─generateUUIDv4(1)────────────────────┬─generateUUIDv4(2)────────────────────┐
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│ 2d49dc6e-ddce-4cd0-afb8-790956df54c1 │ 8abf8c13-7dea-4fdf-af3e-0e18767770e6 │
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└──────────────────────────────────────┴──────────────────────────────────────┘
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```
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## generateUUIDv7 {#generateUUIDv7}
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Generates a [version 7](https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-04) [UUID](../data-types/uuid.md).
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The generated UUID contains the current Unix timestamp in milliseconds (48 bits), followed by version "7" (4 bits), a counter (42 bit) to distinguish UUIDs within a millisecond (including a variant field "2", 2 bit), and a random field (32 bits).
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For any given timestamp (unix_ts_ms), the counter starts at a random value and is incremented by 1 for each new UUID until the timestamp changes.
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In case the counter overflows, the timestamp field is incremented by 1 and the counter is reset to a random new start value.
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Function `generateUUIDv7` guarantees that the counter field within a timestamp increments monotonically across all function invocations in concurrently running threads and queries.
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```
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| unix_ts_ms |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| unix_ts_ms | ver | counter_high_bits |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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|var| counter_low_bits |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| rand_b |
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└─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘
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```
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:::note
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As of April 2024, version 7 UUIDs are in draft status and their layout may change in future.
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:::
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**Syntax**
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``` sql
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generateUUIDv7([expr])
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```
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**Arguments**
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- `expr` — An arbitrary [expression](../syntax.md#syntax-expressions) used to bypass [common subexpression elimination](../functions/index.md#common-subexpression-elimination) if the function is called multiple times in a query. The value of the expression has no effect on the returned UUID. Optional.
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**Returned value**
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A value of type UUIDv7.
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**Example**
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First, create a table with a column of type UUID, then insert a generated UUIDv7 into the table.
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``` sql
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CREATE TABLE tab (uuid UUID) ENGINE = Memory;
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INSERT INTO tab SELECT generateUUIDv7();
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SELECT * FROM tab;
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```
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Result:
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```response
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┌─────────────────────────────────uuid─┐
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│ 018f05af-f4a8-778f-beee-1bedbc95c93b │
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└──────────────────────────────────────┘
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```
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**Example with multiple UUIDs generated per row**
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```sql
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SELECT generateUUIDv7(1), generateUUIDv7(2);
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┌─generateUUIDv7(1)────────────────────┬─generateUUIDv7(2)────────────────────┐
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│ 018f05c9-4ab8-7b86-b64e-c9f03fbd45d1 │ 018f05c9-4ab8-7b86-b64e-c9f12efb7e16 │
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└──────────────────────────────────────┴──────────────────────────────────────┘
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```
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## generateUUIDv7ThreadMonotonic
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Generates a [UUID](../data-types/uuid.md) of [version 7](https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-04).
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The generated UUID contains the current Unix timestamp in milliseconds (48 bits), followed by version "7" (4 bits), a counter (42 bit) to distinguish UUIDs within a millisecond (including a variant field "2", 2 bit), and a random field (32 bits).
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For any given timestamp (unix_ts_ms), the counter starts at a random value and is incremented by 1 for each new UUID until the timestamp changes.
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In case the counter overflows, the timestamp field is incremented by 1 and the counter is reset to a random new start value.
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This function behaves like [generateUUIDv7](#generateUUIDv7) but gives no guarantee on counter monotony across different simultaneous requests.
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Monotonicity within one timestamp is guaranteed only within the same thread calling this function to generate UUIDs.
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```
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| unix_ts_ms |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| unix_ts_ms | ver | counter_high_bits |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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|var| counter_low_bits |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| rand_b |
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└─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘
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```
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:::note
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As of April 2024, version 7 UUIDs are in draft status and their layout may change in future.
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:::
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**Syntax**
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``` sql
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generateUUIDv7ThreadMonotonic([expr])
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```
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**Arguments**
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- `expr` — An arbitrary [expression](../syntax.md#syntax-expressions) used to bypass [common subexpression elimination](../functions/index.md#common-subexpression-elimination) if the function is called multiple times in a query. The value of the expression has no effect on the returned UUID. Optional.
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**Returned value**
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A value of type UUIDv7.
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**Usage example**
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First, create a table with a column of type UUID, then insert a generated UUIDv7 into the table.
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``` sql
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CREATE TABLE tab (uuid UUID) ENGINE = Memory;
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INSERT INTO tab SELECT generateUUIDv7ThreadMonotonic();
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SELECT * FROM tab;
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```
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Result:
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```response
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┌─────────────────────────────────uuid─┐
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│ 018f05e2-e3b2-70cb-b8be-64b09b626d32 │
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└──────────────────────────────────────┘
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```
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**Example with multiple UUIDs generated per row**
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```sql
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SELECT generateUUIDv7ThreadMonotonic(1), generateUUIDv7ThreadMonotonic(2);
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┌─generateUUIDv7ThreadMonotonic(1)─────┬─generateUUIDv7ThreadMonotonic(2)─────┐
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│ 018f05e1-14ee-7bc5-9906-207153b400b1 │ 018f05e1-14ee-7bc5-9906-2072b8e96758 │
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└──────────────────────────────────────┴──────────────────────────────────────┘
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```
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## generateUUIDv7NonMonotonic
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Generates a [UUID](../data-types/uuid.md) of [version 7](https://datatracker.ietf.org/doc/html/draft-peabody-dispatch-new-uuid-format-04).
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The generated UUID contains the current Unix timestamp in milliseconds (48 bits), followed by version "7" (4 bits) and a random field (76 bits, including a 2-bit variant field "2").
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This function is the fastest `generateUUIDv7*` function but it gives no monotonicity guarantees within a timestamp.
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```
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| unix_ts_ms |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| unix_ts_ms | ver | rand_a |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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|var| rand_b |
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├─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┼─┤
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| rand_b |
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└─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┴─┘
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```
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:::note
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As of April 2024, version 7 UUIDs are in draft status and their layout may change in future.
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:::
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**Syntax**
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``` sql
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generateUUIDv7NonMonotonic([expr])
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```
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**Arguments**
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- `expr` — An arbitrary [expression](../syntax.md#syntax-expressions) used to bypass [common subexpression elimination](../functions/index.md#common-subexpression-elimination) if the function is called multiple times in a query. The value of the expression has no effect on the returned UUID. Optional.
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**Returned value**
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A value of type UUIDv7.
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**Example**
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First, create a table with a column of type UUID, then insert a generated UUIDv7 into the table.
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``` sql
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CREATE TABLE tab (uuid UUID) ENGINE = Memory;
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INSERT INTO tab SELECT generateUUIDv7NonMonotonic();
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SELECT * FROM tab;
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```
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Result:
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```response
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┌─────────────────────────────────uuid─┐
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│ 018f05af-f4a8-778f-beee-1bedbc95c93b │
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└──────────────────────────────────────┘
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```
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**Example with multiple UUIDs generated per row**
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```sql
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SELECT generateUUIDv7NonMonotonic(1), generateUUIDv7NonMonotonic(2);
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┌─generateUUIDv7NonMonotonic(1) ───────┬─generateUUIDv7(2)NonMonotonic────────┐
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│ 018f05b1-8c2e-7567-a988-48d09606ae8c │ 018f05b1-8c2e-7946-895b-fcd7635da9a0 │
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└──────────────────────────────────────┴──────────────────────────────────────┘
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```
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## empty
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Checks whether the input UUID is empty.
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**Syntax**
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```sql
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empty(UUID)
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```
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The UUID is considered empty if it contains all zeros (zero UUID).
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The function also works for [Arrays](array-functions.md#function-empty) and [Strings](string-functions.md#empty).
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**Arguments**
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- `x` — A UUID. [UUID](../data-types/uuid.md).
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**Returned value**
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- Returns `1` for an empty UUID or `0` for a non-empty UUID. [UInt8](../data-types/int-uint.md).
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**Example**
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To generate the UUID value, ClickHouse provides the [generateUUIDv4](#uuid-function-generate) function.
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Query:
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```sql
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SELECT empty(generateUUIDv4());
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```
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Result:
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```response
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┌─empty(generateUUIDv4())─┐
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│ 0 │
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└─────────────────────────┘
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```
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## notEmpty
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Checks whether the input UUID is non-empty.
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**Syntax**
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```sql
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notEmpty(UUID)
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```
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The UUID is considered empty if it contains all zeros (zero UUID).
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The function also works for [Arrays](array-functions.md#function-notempty) or [Strings](string-functions.md#notempty).
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**Arguments**
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- `x` — A UUID. [UUID](../data-types/uuid.md).
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**Returned value**
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- Returns `1` for a non-empty UUID or `0` for an empty UUID. [UInt8](../data-types/int-uint.md).
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**Example**
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To generate the UUID value, ClickHouse provides the [generateUUIDv4](#uuid-function-generate) function.
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Query:
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```sql
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SELECT notEmpty(generateUUIDv4());
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```
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Result:
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```response
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┌─notEmpty(generateUUIDv4())─┐
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│ 1 │
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└────────────────────────────┘
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```
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## toUUID
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Converts a value of type String to a UUID.
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``` sql
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toUUID(string)
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```
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**Returned value**
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The UUID type value.
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**Usage example**
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``` sql
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SELECT toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0') AS uuid
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```
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Result:
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```response
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┌─────────────────────────────────uuid─┐
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│ 61f0c404-5cb3-11e7-907b-a6006ad3dba0 │
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└──────────────────────────────────────┘
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```
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## toUUIDOrDefault
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**Arguments**
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- `string` — String of 36 characters or FixedString(36). [String](../syntax.md#string).
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- `default` — UUID to be used as the default if the first argument cannot be converted to a UUID type. [UUID](../data-types/uuid.md).
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**Returned value**
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UUID
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``` sql
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toUUIDOrDefault(string, default)
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```
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**Returned value**
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The UUID type value.
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**Usage examples**
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This first example returns the first argument converted to a UUID type as it can be converted:
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``` sql
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SELECT toUUIDOrDefault('61f0c404-5cb3-11e7-907b-a6006ad3dba0', cast('59f0c404-5cb3-11e7-907b-a6006ad3dba0' as UUID));
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```
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Result:
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```response
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┌─toUUIDOrDefault('61f0c404-5cb3-11e7-907b-a6006ad3dba0', CAST('59f0c404-5cb3-11e7-907b-a6006ad3dba0', 'UUID'))─┐
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│ 61f0c404-5cb3-11e7-907b-a6006ad3dba0 │
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└───────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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This second example returns the second argument (the provided default UUID) as the first argument cannot be converted to a UUID type:
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```sql
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SELECT toUUIDOrDefault('-----61f0c404-5cb3-11e7-907b-a6006ad3dba0', cast('59f0c404-5cb3-11e7-907b-a6006ad3dba0' as UUID));
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```
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Result:
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```response
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┌─toUUIDOrDefault('-----61f0c404-5cb3-11e7-907b-a6006ad3dba0', CAST('59f0c404-5cb3-11e7-907b-a6006ad3dba0', 'UUID'))─┐
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│ 59f0c404-5cb3-11e7-907b-a6006ad3dba0 │
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└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
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```
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## toUUIDOrNull
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Takes an argument of type String and tries to parse it into UUID. If failed, returns NULL.
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``` sql
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toUUIDOrNull(string)
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```
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**Returned value**
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The Nullable(UUID) type value.
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**Usage example**
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``` sql
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SELECT toUUIDOrNull('61f0c404-5cb3-11e7-907b-a6006ad3dba0T') AS uuid
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```
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Result:
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```response
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┌─uuid─┐
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│ ᴺᵁᴸᴸ │
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└──────┘
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```
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## toUUIDOrZero
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It takes an argument of type String and tries to parse it into UUID. If failed, returns zero UUID.
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``` sql
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toUUIDOrZero(string)
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```
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**Returned value**
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The UUID type value.
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**Usage example**
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``` sql
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SELECT toUUIDOrZero('61f0c404-5cb3-11e7-907b-a6006ad3dba0T') AS uuid
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```
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Result:
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```response
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┌─────────────────────────────────uuid─┐
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│ 00000000-0000-0000-0000-000000000000 │
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└──────────────────────────────────────┘
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```
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## UUIDStringToNum
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Accepts `string` containing 36 characters in the format `xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`, and returns a [FixedString(16)](../data-types/fixedstring.md) as its binary representation, with its format optionally specified by `variant` (`Big-endian` by default).
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**Syntax**
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``` sql
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UUIDStringToNum(string[, variant = 1])
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```
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**Arguments**
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- `string` — A [String](../syntax.md#syntax-string-literal) of 36 characters or [FixedString](../syntax.md#syntax-string-literal)
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- `variant` — Integer, representing a variant as specified by [RFC4122](https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.1). 1 = `Big-endian` (default), 2 = `Microsoft`.
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**Returned value**
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FixedString(16)
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**Usage examples**
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``` sql
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SELECT
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'612f3c40-5d3b-217e-707b-6a546a3d7b29' AS uuid,
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UUIDStringToNum(uuid) AS bytes
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```
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Result:
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```response
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┌─uuid─────────────────────────────────┬─bytes────────────┐
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│ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │ a/<@];!~p{jTj={) │
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└──────────────────────────────────────┴──────────────────┘
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```
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``` sql
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SELECT
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'612f3c40-5d3b-217e-707b-6a546a3d7b29' AS uuid,
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UUIDStringToNum(uuid, 2) AS bytes
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```
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Result:
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```response
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┌─uuid─────────────────────────────────┬─bytes────────────┐
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│ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │ @</a;]~!p{jTj={) │
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└──────────────────────────────────────┴──────────────────┘
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```
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## UUIDNumToString
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Accepts `binary` containing a binary representation of a UUID, with its format optionally specified by `variant` (`Big-endian` by default), and returns a string containing 36 characters in text format.
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**Syntax**
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``` sql
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UUIDNumToString(binary[, variant = 1])
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```
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**Arguments**
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- `binary` — [FixedString(16)](../data-types/fixedstring.md) as a binary representation of a UUID.
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- `variant` — Integer, representing a variant as specified by [RFC4122](https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.1). 1 = `Big-endian` (default), 2 = `Microsoft`.
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**Returned value**
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String.
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**Usage example**
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``` sql
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SELECT
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'a/<@];!~p{jTj={)' AS bytes,
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UUIDNumToString(toFixedString(bytes, 16)) AS uuid
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```
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Result:
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```response
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┌─bytes────────────┬─uuid─────────────────────────────────┐
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│ a/<@];!~p{jTj={) │ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │
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└──────────────────┴──────────────────────────────────────┘
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```
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``` sql
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SELECT
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'@</a;]~!p{jTj={)' AS bytes,
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UUIDNumToString(toFixedString(bytes, 16), 2) AS uuid
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```
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Result:
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```response
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┌─bytes────────────┬─uuid─────────────────────────────────┐
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│ @</a;]~!p{jTj={) │ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │
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└──────────────────┴──────────────────────────────────────┘
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```
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## UUIDToNum
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Accepts a [UUID](../data-types/uuid.md) and returns its binary representation as a [FixedString(16)](../data-types/fixedstring.md), with its format optionally specified by `variant` (`Big-endian` by default). This function replaces calls to two separate functions `UUIDStringToNum(toString(uuid))` so no intermediate conversion from UUID to string is required to extract bytes from a UUID.
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**Syntax**
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``` sql
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UUIDToNum(uuid[, variant = 1])
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```
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**Arguments**
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- `uuid` — [UUID](../data-types/uuid.md).
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- `variant` — Integer, representing a variant as specified by [RFC4122](https://datatracker.ietf.org/doc/html/rfc4122#section-4.1.1). 1 = `Big-endian` (default), 2 = `Microsoft`.
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**Returned value**
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The binary representation of the UUID.
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**Usage examples**
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``` sql
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SELECT
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toUUID('612f3c40-5d3b-217e-707b-6a546a3d7b29') AS uuid,
|
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UUIDToNum(uuid) AS bytes
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```
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Result:
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```response
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┌─uuid─────────────────────────────────┬─bytes────────────┐
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│ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │ a/<@];!~p{jTj={) │
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└──────────────────────────────────────┴──────────────────┘
|
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```
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``` sql
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SELECT
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toUUID('612f3c40-5d3b-217e-707b-6a546a3d7b29') AS uuid,
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UUIDToNum(uuid, 2) AS bytes
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```
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Result:
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```response
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┌─uuid─────────────────────────────────┬─bytes────────────┐
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│ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │ @</a;]~!p{jTj={) │
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└──────────────────────────────────────┴──────────────────┘
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```
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## UUIDv7ToDateTime
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Returns the timestamp component of a UUID version 7.
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**Syntax**
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``` sql
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UUIDv7ToDateTime(uuid[, timezone])
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```
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**Arguments**
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- `uuid` — [UUID](../data-types/uuid.md) of version 7.
|
|
- `timezone` — [Timezone name](../../operations/server-configuration-parameters/settings.md#server_configuration_parameters-timezone) for the returned value (optional). [String](../data-types/string.md).
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**Returned value**
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- Timestamp with milliseconds precision. If the UUID is not a valid version 7 UUID, it returns 1970-01-01 00:00:00.000. [DateTime64(3)](../data-types/datetime64.md).
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**Usage examples**
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``` sql
|
|
SELECT UUIDv7ToDateTime(toUUID('018f05c9-4ab8-7b86-b64e-c9f03fbd45d1'))
|
|
```
|
|
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|
Result:
|
|
|
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```response
|
|
┌─UUIDv7ToDateTime(toUUID('018f05c9-4ab8-7b86-b64e-c9f03fbd45d1'))─┐
|
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│ 2024-04-22 15:30:29.048 │
|
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└──────────────────────────────────────────────────────────────────┘
|
|
```
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|
|
``` sql
|
|
SELECT UUIDv7ToDateTime(toUUID('018f05c9-4ab8-7b86-b64e-c9f03fbd45d1'), 'America/New_York')
|
|
```
|
|
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|
Result:
|
|
|
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```response
|
|
┌─UUIDv7ToDateTime(toUUID('018f05c9-4ab8-7b86-b64e-c9f03fbd45d1'), 'America/New_York')─┐
|
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│ 2024-04-22 08:30:29.048 │
|
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└──────────────────────────────────────────────────────────────────────────────────────┘
|
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```
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|
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## serverUUID()
|
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|
|
Returns the random UUID generated during the first start of the ClickHouse server. The UUID is stored in file `uuid` in the ClickHouse server directory (e.g. `/var/lib/clickhouse/`) and retained between server restarts.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
serverUUID()
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
- The UUID of the server. [UUID](../data-types/uuid.md).
|
|
|
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## See also
|
|
|
|
- [dictGetUUID](../functions/ext-dict-functions.md#ext_dict_functions-other)
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