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docs: add some special keywords back

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gccgdb1234 2022-05-31 12:12:49 +08:00
parent 3759ad0ac7
commit eabc276ee7
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41
docs-cn/12-taos-sql/12-keywords/index.md
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@ -85,3 +85,44 @@ title: TDengine 参数限制与保留关键字
| CONNECTIONS | HAVING | NOT | SOFFSET | VNODES |
| CONNS | ID | NOTNULL | STABLE | WAL |
| COPY | IF | NOW | STABLES | WHERE |
| _C0 | _QSTART | _QSTOP | _QDURATION | _WSTART |
| _WSTOP | _WDURATION |
## 特殊说明
### TBNAME
`TBNAME` 可以视为超级表中一个特殊的标签，代表子表的表名。
获取一个超级表所有的子表名及相关的标签信息：
```mysql
SELECT TBNAME, location FROM meters;
统计超级表下辖子表数量：
```mysql
SELECT COUNT(TBNAME) FROM meters;
```
以上两个查询均只支持在WHERE条件子句中添加针对标签（TAGS）的过滤条件。例如：
```mysql
taos> SELECT TBNAME, location FROM meters;
tbname | location |
==================================================================
d1004 | California.SanFrancisco |
d1003 | California.SanFrancisco |
d1002 | California.LosAngeles |
d1001 | California.LosAngeles |
Query OK, 4 row(s) in set (0.000881s)
taos> SELECT COUNT(tbname) FROM meters WHERE groupId > 2;
count(tbname) |
========================
2 |
Query OK, 1 row(s) in set (0.001091s)
```
### _QSTART/_QSTOP/_QDURATION
表示查询过滤窗口的起始，结束以及持续时间 (从2.6.0.0版本开始支持)
### _WSTART/_WSTOP/_WDURATION
窗口切分聚合查询（例如 interval/session window/state window）中表示每个切分窗口的起始，结束以及持续时间（从 2.6.0.0 版本开始支持）
### _c0
表示表或超级表的第一列

41
docs-en/12-taos-sql/12-keywords.md
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@ -46,3 +46,44 @@ There are about 200 keywords reserved by TDengine, they can't be used as the nam
| CONNECTIONS | HAVING | NOT | SOFFSET | VNODES |
| CONNS | ID | NOTNULL | STable | WAL |
| COPY | IF | NOW | STableS | WHERE |
| _C0 | _QSTART | _QSTOP | _QDURATION | _WSTART |
| _WSTOP | _WDURATION |
## Explanations
### TBNAME
`TBNAME` can be considered as a special tag, which represents the name of the subtable, in STable.
Get the table name and tag values of all subtables in a STable.
```mysql
SELECT TBNAME, location FROM meters;
Count the number of subtables in a STable.
```mysql
SELECT COUNT(TBNAME) FROM meters;
```
Only filter on TAGS can be used in WHERE clause in the above two query statements.
```mysql
taos> SELECT TBNAME, location FROM meters;
tbname | location |
==================================================================
d1004 | California.SanFrancisco |
d1003 | California.SanFrancisco |
d1002 | California.LosAngeles |
d1001 | California.LosAngeles |
Query OK, 4 row(s) in set (0.000881s)
taos> SELECT COUNT(tbname) FROM meters WHERE groupId > 2;
count(tbname) |
========================
2 |
Query OK, 1 row(s) in set (0.001091s)
```
### _QSTART/_QSTOP/_QDURATION
The start, stop and duration of a query time window (Since version 2.6.0.0).
### _WSTART/_WSTOP/_WDURATION
The start, stop and duration of aggegate query by time window, like interval, session window, state window (Since version 2.6.0.0).
### _c0
The first column of a table or STable.