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168 lines
4.4 KiB
Markdown
168 lines
4.4 KiB
Markdown
---
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toc_priority: 66
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toc_title: Tuples
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---
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# Functions for Working with Tuples {#tuple-functions}
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## tuple {#tuple}
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A function that allows grouping multiple columns.
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For columns with the types T1, T2, …, it returns a Tuple(T1, T2, …) type tuple containing these columns. There is no cost to execute the function.
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Tuples are normally used as intermediate values for an argument of IN operators, or for creating a list of formal parameters of lambda functions. Tuples can’t be written to a table.
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The function implements the operator `(x, y, …)`.
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**Syntax**
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``` sql
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tuple(x, y, …)
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```
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## tupleElement {#tupleelement}
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A function that allows getting a column from a tuple.
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‘N’ is the column index, starting from 1. N must be a constant. ‘N’ must be a constant. ‘N’ must be a strict postive integer no greater than the size of the tuple.
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There is no cost to execute the function.
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The function implements the operator `x.N`.
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**Syntax**
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``` sql
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tupleElement(tuple, n)
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```
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## untuple {#untuple}
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Performs syntactic substitution of [tuple](../../sql-reference/data-types/tuple.md#tuplet1-t2) elements in the call location.
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**Syntax**
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``` sql
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untuple(x)
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```
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You can use the `EXCEPT` expression to skip columns as a result of the query.
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**Arguments**
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- `x` — A `tuple` function, column, or tuple of elements. [Tuple](../../sql-reference/data-types/tuple.md).
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**Returned value**
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- None.
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**Examples**
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Input table:
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``` text
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┌─key─┬─v1─┬─v2─┬─v3─┬─v4─┬─v5─┬─v6────────┐
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│ 1 │ 10 │ 20 │ 40 │ 30 │ 15 │ (33,'ab') │
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│ 2 │ 25 │ 65 │ 70 │ 40 │ 6 │ (44,'cd') │
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│ 3 │ 57 │ 30 │ 20 │ 10 │ 5 │ (55,'ef') │
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│ 4 │ 55 │ 12 │ 7 │ 80 │ 90 │ (66,'gh') │
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│ 5 │ 30 │ 50 │ 70 │ 25 │ 55 │ (77,'kl') │
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└─────┴────┴────┴────┴────┴────┴───────────┘
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```
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Example of using a `Tuple`-type column as the `untuple` function parameter:
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Query:
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``` sql
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SELECT untuple(v6) FROM kv;
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```
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Result:
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``` text
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┌─_ut_1─┬─_ut_2─┐
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│ 33 │ ab │
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│ 44 │ cd │
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│ 55 │ ef │
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│ 66 │ gh │
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│ 77 │ kl │
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└───────┴───────┘
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```
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Note: the names are implementation specific and are subject to change. You should not assume specific names of the columns after application of the `untuple`.
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Example of using an `EXCEPT` expression:
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Query:
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``` sql
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SELECT untuple((* EXCEPT (v2, v3),)) FROM kv;
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```
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Result:
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``` text
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┌─key─┬─v1─┬─v4─┬─v5─┬─v6────────┐
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│ 1 │ 10 │ 30 │ 15 │ (33,'ab') │
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│ 2 │ 25 │ 40 │ 6 │ (44,'cd') │
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│ 3 │ 57 │ 10 │ 5 │ (55,'ef') │
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│ 4 │ 55 │ 80 │ 90 │ (66,'gh') │
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│ 5 │ 30 │ 25 │ 55 │ (77,'kl') │
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└─────┴────┴────┴────┴───────────┘
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```
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**See Also**
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- [Tuple](../../sql-reference/data-types/tuple.md)
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## tupleHammingDistance {#tuplehammingdistance}
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Returns the [Hamming Distance](https://en.wikipedia.org/wiki/Hamming_distance) between two tuples of the same size.
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**Syntax**
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``` sql
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tupleHammingDistance(tuple1, tuple2)
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```
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**Arguments**
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- `tuple1` — First tuple. [Tuple](../../sql-reference/data-types/tuple.md).
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- `tuple2` — Second tuple. [Tuple](../../sql-reference/data-types/tuple.md).
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Tuples should have the same type of the elements.
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**Returned value**
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- The Hamming distance.
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Type: [UInt8](../../sql-reference/data-types/int-uint.md).
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**Examples**
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Query:
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``` sql
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SELECT tupleHammingDistance((1, 2, 3), (3, 2, 1)) AS HammingDistance;
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```
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Result:
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``` text
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┌─HammingDistance─┐
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│ 2 │
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└─────────────────┘
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```
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Can be used with [MinHash](../../sql-reference/functions/hash-functions.md#ngramminhash) functions for detection of semi-duplicate strings:
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``` sql
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SELECT tupleHammingDistance(wordShingleMinHash(string), wordShingleMinHashCaseInsensitive(string)) as HammingDistance FROM (SELECT 'ClickHouse is a column-oriented database management system for online analytical processing of queries.' AS string);
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```
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Result:
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``` text
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┌─HammingDistance─┐
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│ 2 │
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└─────────────────┘
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```
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