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docs: add tags keyword in select clause #22570

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Aug 25, 2023
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docs: add tags keyword in select clause
shenglian-zhou Aug 25, 2023
7958fdf
Update 06-select.md
dapan1121 Aug 25, 2023
470b37b
Update 06-select.md
dapan1121 Aug 25, 2023
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10 changes: 9 additions & 1 deletion docs/en/12-taos-sql/06-select.md
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,7 @@ description: This document describes how to query data in TDengine.
```sql
SELECT {DATABASE() | CLIENT_VERSION() | SERVER_VERSION() | SERVER_STATUS() | NOW() | TODAY() | TIMEZONE()}

SELECT [hints] [DISTINCT] select_list
SELECT [hints] [DISTINCT] [TAGS] select_list
from_clause
[WHERE condition]
[partition_by_clause]
Expand Down Expand Up @@ -225,6 +225,14 @@ The \_IROWTS pseudocolumn can only be used with INTERP function. This pseudocolu
select _irowts, interp(current) from meters range('2020-01-01 10:00:00', '2020-01-01 10:30:00') every(1s) fill(linear);
```

### TAGS Query

The TAGS keyword returns only tag columns from all child tables when only tag columns are specified. One row containing tag columns is returned for each child table.

```sql
SELECT TAGS tag_name [, tag_name ...] FROM stb_name
```

## Query Objects

`FROM` can be followed by a number of tables or super tables, or can be followed by a sub-query.
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12 changes: 11 additions & 1 deletion docs/zh/12-taos-sql/06-select.md
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Expand Up @@ -9,7 +9,7 @@ description: 查询数据的详细语法
```sql
SELECT {DATABASE() | CLIENT_VERSION() | SERVER_VERSION() | SERVER_STATUS() | NOW() | TODAY() | TIMEZONE()}

SELECT [hints] [DISTINCT] select_list
SELECT [hints] [DISTINCT] [TAGS] select_list
from_clause
[WHERE condition]
[partition_by_clause]
Expand Down Expand Up @@ -160,6 +160,16 @@ SELECT DISTINCT col_name [, col_name ...] FROM tb_name;

:::

### 标签查询

当查询的列只有标签列时，`TAGS` 关键字可以指定返回所有子表的标签列。每个子表只返回一行标签列。

返回所有子表的标签列：

```sql
SELECT TAGS tag_name [, tag_name ...] FROM stb_name
```

### 结果集列名

`SELECT`子句中，如果不指定返回结果集合的列名，结果集列名称默认使用`SELECT`子句中的表达式名称作为列名称。此外，用户可使用`AS`来重命名返回结果集合中列的名称。例如：
Expand Down