From eabc276ee7933cf540156bf8e35891e972af89f8 Mon Sep 17 00:00:00 2001 From: gccgdb1234 Date: Tue, 31 May 2022 12:12:49 +0800 Subject: [PATCH] docs: add some special keywords back --- docs-cn/12-taos-sql/12-keywords/index.md | 41 ++++++++++++++++++++++++ docs-en/12-taos-sql/12-keywords.md | 41 ++++++++++++++++++++++++ 2 files changed, 82 insertions(+) diff --git a/docs-cn/12-taos-sql/12-keywords/index.md b/docs-cn/12-taos-sql/12-keywords/index.md index a64a7161d0..0b9ec4de86 100644 --- a/docs-cn/12-taos-sql/12-keywords/index.md +++ b/docs-cn/12-taos-sql/12-keywords/index.md @@ -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 \ No newline at end of file diff --git a/docs-en/12-taos-sql/12-keywords.md b/docs-en/12-taos-sql/12-keywords.md index fa750300b7..56a82a02a1 100644 --- a/docs-en/12-taos-sql/12-keywords.md +++ b/docs-en/12-taos-sql/12-keywords.md @@ -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. \ No newline at end of file