mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-12-16 19:32:07 +00:00
267 lines
6.2 KiB
Markdown
267 lines
6.2 KiB
Markdown
---
|
|
toc_priority: 53
|
|
toc_title: UUID
|
|
---
|
|
|
|
# Functions for Working with UUID {#functions-for-working-with-uuid}
|
|
|
|
The functions for working with UUID are listed below.
|
|
|
|
## generateUUIDv4 {#uuid-function-generate}
|
|
|
|
Generates the [UUID](../data-types/uuid.md) of [version 4](https://tools.ietf.org/html/rfc4122#section-4.4).
|
|
|
|
``` sql
|
|
generateUUIDv4()
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
The UUID type value.
|
|
|
|
**Usage example**
|
|
|
|
This example demonstrates creating a table with the UUID type column and inserting a value into the table.
|
|
|
|
``` sql
|
|
CREATE TABLE t_uuid (x UUID) ENGINE=TinyLog
|
|
|
|
INSERT INTO t_uuid SELECT generateUUIDv4()
|
|
|
|
SELECT * FROM t_uuid
|
|
```
|
|
|
|
``` text
|
|
┌────────────────────────────────────x─┐
|
|
│ f4bf890f-f9dc-4332-ad5c-0c18e73f28e9 │
|
|
└──────────────────────────────────────┘
|
|
```
|
|
|
|
## empty {#empty}
|
|
|
|
Checks whether the input UUID is empty.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
empty(UUID)
|
|
```
|
|
|
|
The UUID is considered empty if it contains all zeros (zero UUID).
|
|
|
|
The function also works for [arrays](array-functions.md#function-empty) or [strings](string-functions.md#empty).
|
|
|
|
**Arguments**
|
|
|
|
- `x` — Input UUID. [UUID](../data-types/uuid.md).
|
|
|
|
**Returned value**
|
|
|
|
- Returns `1` for an empty UUID or `0` for a non-empty UUID.
|
|
|
|
Type: [UInt8](../data-types/int-uint.md).
|
|
|
|
**Example**
|
|
|
|
To generate the UUID value, ClickHouse provides the [generateUUIDv4](#uuid-function-generate) function.
|
|
|
|
Query:
|
|
|
|
```sql
|
|
SELECT empty(generateUUIDv4());
|
|
```
|
|
|
|
Result:
|
|
|
|
```text
|
|
┌─empty(generateUUIDv4())─┐
|
|
│ 0 │
|
|
└─────────────────────────┘
|
|
```
|
|
|
|
## notEmpty {#notempty}
|
|
|
|
Checks whether the input UUID is non-empty.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
notEmpty(UUID)
|
|
```
|
|
|
|
The UUID is considered empty if it contains all zeros (zero UUID).
|
|
|
|
The function also works for [arrays](array-functions.md#function-notempty) or [strings](string-functions.md#notempty).
|
|
|
|
**Arguments**
|
|
|
|
- `x` — Input UUID. [UUID](../data-types/uuid.md).
|
|
|
|
**Returned value**
|
|
|
|
- Returns `1` for a non-empty UUID or `0` for an empty UUID.
|
|
|
|
Type: [UInt8](../data-types/int-uint.md).
|
|
|
|
**Example**
|
|
|
|
To generate the UUID value, ClickHouse provides the [generateUUIDv4](#uuid-function-generate) function.
|
|
|
|
Query:
|
|
|
|
```sql
|
|
SELECT notEmpty(generateUUIDv4());
|
|
```
|
|
|
|
Result:
|
|
|
|
```text
|
|
┌─notEmpty(generateUUIDv4())─┐
|
|
│ 1 │
|
|
└────────────────────────────┘
|
|
```
|
|
|
|
## toUUID (x) {#touuid-x}
|
|
|
|
Converts String type value to UUID type.
|
|
|
|
``` sql
|
|
toUUID(String)
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
The UUID type value.
|
|
|
|
**Usage example**
|
|
|
|
``` sql
|
|
SELECT toUUID('61f0c404-5cb3-11e7-907b-a6006ad3dba0') AS uuid
|
|
```
|
|
|
|
``` text
|
|
┌─────────────────────────────────uuid─┐
|
|
│ 61f0c404-5cb3-11e7-907b-a6006ad3dba0 │
|
|
└──────────────────────────────────────┘
|
|
```
|
|
|
|
## toUUIDOrNull (x) {#touuidornull-x}
|
|
|
|
It takes an argument of type String and tries to parse it into UUID. If failed, returns NULL.
|
|
|
|
``` sql
|
|
toUUIDOrNull(String)
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
The Nullable(UUID) type value.
|
|
|
|
**Usage example**
|
|
|
|
``` sql
|
|
SELECT toUUIDOrNull('61f0c404-5cb3-11e7-907b-a6006ad3dba0T') AS uuid
|
|
```
|
|
|
|
``` text
|
|
┌─uuid─┐
|
|
│ ᴺᵁᴸᴸ │
|
|
└──────┘
|
|
```
|
|
|
|
## toUUIDOrZero (x) {#touuidorzero-x}
|
|
|
|
It takes an argument of type String and tries to parse it into UUID. If failed, returns zero UUID.
|
|
|
|
``` sql
|
|
toUUIDOrZero(String)
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
The UUID type value.
|
|
|
|
**Usage example**
|
|
|
|
``` sql
|
|
SELECT toUUIDOrZero('61f0c404-5cb3-11e7-907b-a6006ad3dba0T') AS uuid
|
|
```
|
|
|
|
``` text
|
|
┌─────────────────────────────────uuid─┐
|
|
│ 00000000-0000-0000-0000-000000000000 │
|
|
└──────────────────────────────────────┘
|
|
```
|
|
|
|
## UUIDStringToNum {#uuidstringtonum}
|
|
|
|
Accepts a string containing 36 characters in the format `xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx`, and returns it as a set of bytes in a [FixedString(16)](../../sql-reference/data-types/fixedstring.md).
|
|
|
|
``` sql
|
|
UUIDStringToNum(String)
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
FixedString(16)
|
|
|
|
**Usage examples**
|
|
|
|
``` sql
|
|
SELECT
|
|
'612f3c40-5d3b-217e-707b-6a546a3d7b29' AS uuid,
|
|
UUIDStringToNum(uuid) AS bytes
|
|
```
|
|
|
|
``` text
|
|
┌─uuid─────────────────────────────────┬─bytes────────────┐
|
|
│ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │ a/<@];!~p{jTj={) │
|
|
└──────────────────────────────────────┴──────────────────┘
|
|
```
|
|
|
|
## UUIDNumToString {#uuidnumtostring}
|
|
|
|
Accepts a [FixedString(16)](../../sql-reference/data-types/fixedstring.md) value, and returns a string containing 36 characters in text format.
|
|
|
|
``` sql
|
|
UUIDNumToString(FixedString(16))
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
String.
|
|
|
|
**Usage example**
|
|
|
|
``` sql
|
|
SELECT
|
|
'a/<@];!~p{jTj={)' AS bytes,
|
|
UUIDNumToString(toFixedString(bytes, 16)) AS uuid
|
|
```
|
|
|
|
``` text
|
|
┌─bytes────────────┬─uuid─────────────────────────────────┐
|
|
│ a/<@];!~p{jTj={) │ 612f3c40-5d3b-217e-707b-6a546a3d7b29 │
|
|
└──────────────────┴──────────────────────────────────────┘
|
|
```
|
|
|
|
## serverUUID() {#server-uuid}
|
|
|
|
Returns the random and unique UUID, which is generated when the server is first started and stored forever. The result writes to the file `uuid` created in the ClickHouse server directory `/var/lib/clickhouse/`.
|
|
|
|
**Syntax**
|
|
|
|
```sql
|
|
serverUUID()
|
|
```
|
|
|
|
**Returned value**
|
|
|
|
- The UUID of the server.
|
|
|
|
Type: [UUID](../data-types/uuid.md).
|
|
|
|
## See Also {#see-also}
|
|
|
|
- [dictGetUUID](../../sql-reference/functions/ext-dict-functions.md#ext_dict_functions-other)
|