允许对查询中外层表表达式返回的每一行调用某个函数。
语法
SELECT <expr> APPLY( <func> ) FROM [db.]table_name
示例
CREATE TABLE columns_transformers (i Int64, j Int16, k Int64) ENGINE = MergeTree ORDER by (i);
INSERT INTO columns_transformers VALUES (100, 10, 324), (120, 8, 23);
SELECT * APPLY(sum) FROM columns_transformers;
┌─sum(i)─┬─sum(j)─┬─sum(k)─┐
│ 220 │ 18 │ 347 │
└────────┴────────┴────────┘