Merge pull request #17129 from taosdata/docs/irowts
docs: add _irowts pseudocolumn description in ZN/EN docs
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wade zhang
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@ -181,6 +181,14 @@ In TDengine, the first column of all tables must be a timestamp. This column is
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select _rowts, max(current) from meters;
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```
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**\_IROWTS**
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The \_IROWTS pseudocolumn can only be used with INTERP function. This pseudocolumn can be used to retrieve the corresponding timestamp column associated with the interpolation results.
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```sql
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select _irowts, interp(current) from meters range('2020-01-01 10:00:00', '2020-01-01 10:30:00') every(1s) fill(linear);
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```
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## Query Objects
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`FROM` can be followed by a number of tables or super tables, or can be followed by a sub-query.
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@ -343,6 +343,7 @@ The following list shows all reserved keywords:
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### \_
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- \_C0
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- \_IROWTS
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- \_QDURATION
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- \_QEND
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- \_QSTART
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@ -11,12 +11,13 @@ description: "This document explains how TDengine SQL has changed in version 3.0
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| 1 | VARCHAR | Added | Alias of BINARY.
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| 2 | TIMESTAMP literal | Added | TIMESTAMP 'timestamp format' syntax now supported.
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| 3 | _ROWTS pseudocolumn | Added | Indicates the primary key. Alias of _C0.
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| 4 | INFORMATION_SCHEMA | Added | Database for system metadata containing all schema definitions
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| 5 | PERFORMANCE_SCHEMA | Added | Database for system performance information.
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| 6 | Connection queries | Deprecated | Connection queries are no longer supported. The syntax and interfaces are deprecated.
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| 7 | Mixed operations | Enhanced | Mixing scalar and vector operations in queries has been enhanced and is supported in all SELECT clauses.
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| 8 | Tag operations | Added | Tag columns can be used in queries and clauses like data columns.
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| 9 | Timeline clauses and time functions in supertables | Enhanced | When PARTITION BY is not used, data in supertables is merged into a single timeline.
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| 4 | _IROWTS pseudocolumn | Added | Used to retrieve timestamps with INTERP function.
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| 5 | INFORMATION_SCHEMA | Added | Database for system metadata containing all schema definitions
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| 6 | PERFORMANCE_SCHEMA | Added | Database for system performance information.
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| 7 | Connection queries | Deprecated | Connection queries are no longer supported. The syntax and interfaces are deprecated.
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| 8 | Mixed operations | Enhanced | Mixing scalar and vector operations in queries has been enhanced and is supported in all SELECT clauses.
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| 9 | Tag operations | Added | Tag columns can be used in queries and clauses like data columns.
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| 10 | Timeline clauses and time functions in supertables | Enhanced | When PARTITION BY is not used, data in supertables is merged into a single timeline.
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## SQL Syntax
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@ -182,6 +182,14 @@ TDengine 中，所有表的第一列都必须是时间戳类型，且为其主
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select _rowts, max(current) from meters;
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```
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**\_IROWTS**
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\_irowts 伪列只能与 interp 函数一起使用，用于返回 interp 函数插值结果对应的时间戳列。
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```sql
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select _irowts, interp(current) from meters range('2020-01-01 10:00:00', '2020-01-01 10:30:00') every(1s) fill(linear);
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```
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## 查询对象
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FROM 关键字后面可以是若干个表（超级表）列表，也可以是子查询的结果。
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@ -344,6 +344,7 @@ description: TDengine 保留关键字的详细列表
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### \_
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- \_C0
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- \_IROWTS
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- \_QDURATION
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- \_QEND
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- \_QSTART
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@ -11,12 +11,13 @@ description: "TDengine 3.0 版本的语法变更说明"
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| 1 | VARCHAR | 新增 | BINARY类型的别名。
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| 2 | TIMESTAMP字面量 | 新增 | 新增支持 TIMESTAMP 'timestamp format' 语法。
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| 3 | _ROWTS伪列 | 新增 | 表示时间戳主键。是_C0伪列的别名。
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| 4 | INFORMATION_SCHEMA | 新增 | 包含各种SCHEMA定义的系统数据库。
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| 5 | PERFORMANCE_SCHEMA | 新增 | 包含运行信息的系统数据库。
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| 6 | 连续查询 | 废除 | 不再支持连续查询。相关的各种语法和接口废除。
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| 7 | 混合运算 | 增强 | 查询中的混合运算（标量运算和矢量运算混合）全面增强，SELECT的各个子句均全面支持符合语法语义的混合运算。
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| 8 | 标签运算 | 新增 |在查询中，标签列可以像普通列一样参与各种运算，用于各种子句。
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| 9 | 时间线子句和时间函数用于超级表查询 | 增强 |没有PARTITION BY时，超级表的数据会被合并成一条时间线。
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| 4 | _IROWTS伪列 | 新增 | 用于返回 interp 函数插值结果对应的时间戳列。
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| 5 | INFORMATION_SCHEMA | 新增 | 包含各种SCHEMA定义的系统数据库。
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| 6 | PERFORMANCE_SCHEMA | 新增 | 包含运行信息的系统数据库。
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| 7 | 连续查询 | 废除 | 不再支持连续查询。相关的各种语法和接口废除。
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| 8 | 混合运算 | 增强 | 查询中的混合运算（标量运算和矢量运算混合）全面增强，SELECT的各个子句均全面支持符合语法语义的混合运算。
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| 9 | 标签运算 | 新增 |在查询中，标签列可以像普通列一样参与各种运算，用于各种子句。
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| 10 | 时间线子句和时间函数用于超级表查询 | 增强 |没有PARTITION BY时，超级表的数据会被合并成一条时间线。
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## SQL 语句变更
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