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2e1f6bc56d
* replace exit with assert in test_single_page * improve save_raw_single_page docs option * More grammar fixes * "Built from" link in new tab * fix mistype * Example of include in docs * add anchor to meeting form * Draft of translation helper * WIP on translation helper * Replace some fa docs content with machine translation * add normalize-en-markdown.sh * normalize some en markdown * normalize some en markdown * admonition support * normalize * normalize * normalize * support wide tables * normalize * normalize * normalize * normalize * normalize * normalize * normalize * normalize * normalize * normalize * normalize * normalize * normalize * lightly edited machine translation of introdpection.md * lightly edited machhine translation of lazy.md * WIP on translation utils * Normalize ru docs * Normalize other languages * some fixes * WIP on normalize/translate tools * add requirements.txt * [experimental] add es docs language as machine translated draft * remove duplicate script * Back to wider tab-stop (narrow renders not so well)
1.4 KiB
1.4 KiB
条件函数
if(cond, then, else), cond ? operator then : else
如果cond ！= 0则返回then，如果cond = 0则返回else。
cond必须是UInt8类型，then和else必须存在最低的共同类型。
then和else可以是NULL
multiIf
允许您在查询中更紧凑地编写CASE运算符。
multiIf(cond_1, then_1, cond_2, then_2...else)
参数:
cond_N— 函数返回then_N的条件。then_N— 执行时函数的结果。else— 如果没有满足任何条件，则为函数的结果。
该函数接受2N + 1参数。
返回值
该函数返回值«then_N»或«else»之一，具体取决于条件cond_N。
示例
存在如下一张表
┌─x─┬────y─┐
│ 1 │ ᴺᵁᴸᴸ │
│ 2 │ 3 │
└───┴──────┘
执行查询 SELECT multiIf(isNull(y) x, y < 3, y, NULL) FROM t_null。结果：
┌─multiIf(isNull(y), x, less(y, 3), y, NULL)─┐
│ 1 │
│ ᴺᵁᴸᴸ │
└────────────────────────────────────────────┘