mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-27 18:12:02 +00:00
8623cb232c
* CLICKHOUSE-4063: less manual html @ index.md * CLICKHOUSE-4063: recommend markdown="1" in README.md * CLICKHOUSE-4003: manually purge custom.css for now * CLICKHOUSE-4064: expand <details> before any print (including to pdf) * CLICKHOUSE-3927: rearrange interfaces/formats.md a bit * CLICKHOUSE-3306: add few http headers * Remove copy-paste introduced in #3392 * Hopefully better chinese fonts #3392 * get rid of tabs @ custom.css * Apply comments and patch from #3384 * Add jdbc.md to ToC and some translation, though it still looks badly incomplete * minor punctuation * Add some backlinks to official website from mirrors that just blindly take markdown sources * Do not make fonts extra light * find . -name '*.md' -type f | xargs -I{} perl -pi -e 's//g' {} * find . -name '*.md' -type f | xargs -I{} perl -pi -e 's/ sql/g' {} * Remove outdated stuff from roadmap.md * Not so light font on front page too * Refactor Chinese formats.md to match recent changes in other languages
51 lines
1.4 KiB
Markdown
51 lines
1.4 KiB
Markdown
# Conditional functions
|
|
|
|
## if(cond, then, else), cond ? operator then : else
|
|
|
|
Returns `then` if `cond != 0`, or `else` if `cond = 0`.
|
|
`cond` must be of type `UInt8`, and `then` and `else` must have the lowest common type.
|
|
|
|
`then` and `else` can be `NULL`
|
|
|
|
## multiIf
|
|
|
|
Allows you to write the [CASE](../operators.md#operator_case) operator more compactly in the query.
|
|
|
|
```
|
|
multiIf(cond_1, then_1, cond_2, then_2...else)
|
|
```
|
|
|
|
**Parameters:**
|
|
|
|
- `cond_N` — The condition for the function to return `then_N`.
|
|
- `then_N` — The result of the function when executed.
|
|
- `else` — The result of the function if none of the conditions is met.
|
|
|
|
The function accepts `2N+1` parameters.
|
|
|
|
**Returned values**
|
|
|
|
The function returns one of the values `then_N` or `else`, depending on the conditions `cond_N`.
|
|
|
|
**Example**
|
|
|
|
Take the table
|
|
|
|
```
|
|
┌─x─┬────y─┐
|
|
│ 1 │ ᴺᵁᴸᴸ │
|
|
│ 2 │ 3 │
|
|
└───┴──────┘
|
|
```
|
|
|
|
Run the query `SELECT multiIf(isNull(y) x, y < 3, y, NULL) FROM t_null`. Result:
|
|
|
|
```
|
|
┌─multiIf(isNull(y), x, less(y, 3), y, NULL)─┐
|
|
│ 1 │
|
|
│ ᴺᵁᴸᴸ │
|
|
└────────────────────────────────────────────┘
|
|
```
|
|
|
|
[Original article](https://clickhouse.yandex/docs/en/query_language/functions/conditional_functions/) <!--hide-->
|