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51 lines
1.4 KiB
Markdown
51 lines
1.4 KiB
Markdown
# Conditional functions
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## if(cond, then, else), cond ? operator then : else
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Returns `then` if `cond != 0`, or `else` if `cond = 0`.
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`cond` must be of type `UInt8`, and `then` and `else` must have the lowest common type.
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`then` and `else` can be `NULL`
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## multiIf
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Allows you to write the [CASE](../operators.md#operator_case) operator more compactly in the query.
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```
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multiIf(cond_1, then_1, cond_2, then_2...else)
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```
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**Parameters:**
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- `cond_N` — The condition for the function to return `then_N`.
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- `then_N` — The result of the function when executed.
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- `else` — The result of the function if none of the conditions is met.
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The function accepts `2N+1` parameters.
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**Returned values**
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The function returns one of the values `then_N` or `else`, depending on the conditions `cond_N`.
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**Example**
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Take the table
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```
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┌─x─┬────y─┐
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│ 1 │ ᴺᵁᴸᴸ │
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│ 2 │ 3 │
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└───┴──────┘
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```
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Run the query `SELECT multiIf(isNull(y) x, y < 3, y, NULL) FROM t_null`. Result:
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```
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┌─multiIf(isNull(y), x, less(y, 3), y, NULL)─┐
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│ 1 │
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│ ᴺᵁᴸᴸ │
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└────────────────────────────────────────────┘
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```
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[Original article](https://clickhouse.yandex/docs/en/query_language/functions/conditional_functions/) <!--hide-->
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