> ## Documentation Index
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> Use this file to discover all available pages before exploring further.

> 介绍 APPLY 修饰符的文档；该修饰符允许对查询中外层表表达式返回的每一行调用某个函数。

# APPLY 修饰符

> 允许对查询中外层表表达式返回的每一行调用某个函数。

<div id="syntax">
  ## 语法
</div>

```sql theme={null}
SELECT <expr> APPLY( <func> ) FROM [db.]table_name
```

<div id="example">
  ## 示例
</div>

```sql theme={null}
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;
```

```response theme={null}
┌─sum(i)─┬─sum(j)─┬─sum(k)─┐
│    220 │     18 │    347 │
└────────┴────────┴────────┘
```