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Merge pull request #23228 from taosdata/doc/3.0/TD-25620 

add doc for sort_for_group hint
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dapan1121 2023-10-12 08:26:52 +08:00 committed by GitHub
parent ee7258bb59 b9cabf3158
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2 changed files with 14 additions and 10 deletions
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12
docs/en/12-taos-sql/06-select.md
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@ -24,7 +24,7 @@ SELECT [hints] [DISTINCT] select_list
hints: /*+ [hint([hint_param_list])] [hint([hint_param_list])] */
hint:
BATCH_SCAN | NO_BATCH_SCAN
BATCH_SCAN | NO_BATCH_SCAN | SORT_FOR_GROUP
select_list:
select_expr [, select_expr] ...
@ -87,15 +87,17 @@ Hints are a means of user control over query optimization for individual stateme
The list of currently supported Hints is as follows:
| **Hint** | **Params** | **Comment** | **Scopt** |
| :-----------: | -------------- | -------------------------- | -------------------------- |
| BATCH_SCAN | None | Batch table scan | JOIN statment for stable |
| NO_BATCH_SCAN | None | Sequential table scan | JOIN statment for stable |
| **Hint** | **Params** | **Comment** | **Scopt** |
| :-----------: | -------------- | -------------------------- | -----------------------------------|
| BATCH_SCAN | None | Batch table scan | JOIN statment for stable |
| NO_BATCH_SCAN | None | Sequential table scan | JOIN statment for stable |
| SORT_FOR_GROUP| None | Use sort for partition | With normal column in partition by list |
For example:
```sql
SELECT /*+ BATCH_SCAN() */ a.ts FROM stable1 a, stable2 b where a.tag0 = b.tag0 and a.ts = b.ts;
SELECT /*+ SORT_FOR_GROUP() */ count(*), c1 FROM stable1 PARTITION BY c1;
```
## Lists

12
docs/zh/12-taos-sql/06-select.md
View File

@ -24,7 +24,7 @@ SELECT [hints] [DISTINCT] select_list
hints: /*+ [hint([hint_param_list])] [hint([hint_param_list])] */
hint:
BATCH_SCAN | NO_BATCH_SCAN
BATCH_SCAN | NO_BATCH_SCAN | SORT_FOR_GROUP
select_list:
select_expr [, select_expr] ...
@ -87,15 +87,17 @@ Hints 是用户控制单个语句查询优化的一种手段，当 Hint 不适
目前支持的 Hints 列表如下：
| **Hint** | **参数** | **说明** | **适用范围** |
| :-----------: | -------------- | -------------------------- | -------------------------- |
| BATCH_SCAN | 无 | 采用批量读表的方式 | 超级表 JOIN 语句 |
| NO_BATCH_SCAN | 无 | 采用顺序读表的方式 | 超级表 JOIN 语句 |
| **Hint** | **参数** | **说明** | **适用范围** |
| :-----------: | -------------- | -------------------------- | -----------------------------|
| BATCH_SCAN | 无 | 采用批量读表的方式 | 超级表 JOIN 语句 |
| NO_BATCH_SCAN | 无 | 采用顺序读表的方式 | 超级表 JOIN 语句 |
| SORT_FOR_GROUP| 无 | 采用sort方式进行分组 | partition by 列表有普通列时 |
举例：
```sql
SELECT /*+ BATCH_SCAN() */ a.ts FROM stable1 a, stable2 b where a.tag0 = b.tag0 and a.ts = b.ts;
SELECT /*+ SORT_FOR_GROUP() */ count(*), c1 FROM stable1 PARTITION BY c1;
```
## 列表