diff --git a/src/.vuepress/sidebar/V2.0.x/en-Table.ts b/src/.vuepress/sidebar/V2.0.x/en-Table.ts index 73eee9bcd..31cf39b91 100644 --- a/src/.vuepress/sidebar/V2.0.x/en-Table.ts +++ b/src/.vuepress/sidebar/V2.0.x/en-Table.ts @@ -235,6 +235,7 @@ export const enSidebar = { collapsible: true, children: [ { text: 'overview', link: 'overview_apache' }, + { text: 'Tableless Query', link: 'Tableless-Query_apache' }, { text: 'SELECT Clause', link: 'Select-Clause_apache' }, { text: 'FROM&JOIN Clause', link: 'From-Join-Clause' }, { text: 'WHERE Clause', link: 'Where-Clause' }, diff --git a/src/.vuepress/sidebar/V2.0.x/zh-Table.ts b/src/.vuepress/sidebar/V2.0.x/zh-Table.ts index a1f69708b..aab73d213 100644 --- a/src/.vuepress/sidebar/V2.0.x/zh-Table.ts +++ b/src/.vuepress/sidebar/V2.0.x/zh-Table.ts @@ -235,6 +235,7 @@ export const zhSidebar = { collapsible: true, children: [ { text: '概览', link: 'overview_apache' }, + { text: '无表查询', link: 'Tableless-Query_apache' }, { text: 'SELECT子句', link: 'Select-Clause_apache' }, { text: 'FROM&JOIN子句', link: 'From-Join-Clause' }, { text: 'WHERE子句', link: 'Where-Clause' }, diff --git a/src/UserGuide/Master/Table/SQL-Manual/Tableless-Query_apache.md b/src/UserGuide/Master/Table/SQL-Manual/Tableless-Query_apache.md new file mode 100644 index 000000000..d75d4f2ef --- /dev/null +++ b/src/UserGuide/Master/Table/SQL-Manual/Tableless-Query_apache.md @@ -0,0 +1,131 @@ + + +# Tableless Query + +## 1. Overview + +Tableless query allows you to execute SQL statements without a `FROM` clause, without relying on any actual database table. It retrieves computed results, constant values, or system information, and is mainly used in scenarios such as expression evaluation, system function calls, and constant queries. + +> Note: This feature is supported since V2.0.11. + +## 2. Syntax + +```sql +SELECT expression [ [ AS ] column_alias ] + [, expression [ [ AS ] column_alias ] ]*; +``` + +Where: + +- `expression`: the expression to be evaluated. It can be a constant, a mathematical function, a string function, a date-time function, or an aggregate function. Currently, only functions that take **no arguments or constant arguments only** are supported. + +- `column_alias`: an optional alias for the result column, which improves the readability of query results. If no alias is specified, the system automatically generates column names such as `_col0`, `_col1`, etc. + +- `SELECT *` is not supported. + +- When executing `SELECT COUNT(*);`, the result is always `1`. + +## 3. Examples + +### 3.1 Constants and Mathematical Calculations + +Query statement: + +```sql +SELECT 100 + 50 AS sum_result, + 10 * 5 AS product, + SQRT(144) AS square_root, + ABS(-25) AS absolute_value, + SIN(1) AS sin_value; +``` + +Result: + +```text ++----------+-------+-----------+--------------+------------------+ +|sum_result|product|square_root|absolute_value| sin_value| ++----------+-------+-----------+--------------+------------------+ +| 150| 50| 12.0| 25|0.8414709848078965| ++----------+-------+-----------+--------------+------------------+ +``` + +### 3.2 String Functions + +Query statement: + +```sql +SELECT + CONCAT('Hello', ' ', 'World') AS greeting, + UPPER('iotdb') AS uppercase, + LOWER('IOTDB') AS lowercase, + LENGTH('database') AS str_length; +``` + +Result: + +```text ++-----------+---------+---------+----------+ +| greeting|uppercase|lowercase|str_length| ++-----------+---------+---------+----------+ +|Hello World| IOTDB| iotdb| 8| ++-----------+---------+---------+----------+ +``` + +### 3.3 Date and Time Functions + +Query statement: + +```sql +SELECT NOW() AS now_time; +``` + +Result: + +```text ++-------------+ +| now_time| ++-------------+ +|1784776724555| ++-------------+ +``` + +### 3.4 Aggregate Functions + +Query statement: + +```sql +SELECT + AVG(10), + SUM(10), + COUNT(10), + COUNT(*); +``` + +Result: + +```text ++-----+-----+-----+-----+ +|_col0|_col1|_col2|_col3| ++-----+-----+-----+-----+ +| 10.0| 10.0| 1| 1| ++-----+-----+-----+-----+ +``` diff --git a/src/UserGuide/latest-Table/SQL-Manual/Tableless-Query_apache.md b/src/UserGuide/latest-Table/SQL-Manual/Tableless-Query_apache.md new file mode 100644 index 000000000..d75d4f2ef --- /dev/null +++ b/src/UserGuide/latest-Table/SQL-Manual/Tableless-Query_apache.md @@ -0,0 +1,131 @@ + + +# Tableless Query + +## 1. Overview + +Tableless query allows you to execute SQL statements without a `FROM` clause, without relying on any actual database table. It retrieves computed results, constant values, or system information, and is mainly used in scenarios such as expression evaluation, system function calls, and constant queries. + +> Note: This feature is supported since V2.0.11. + +## 2. Syntax + +```sql +SELECT expression [ [ AS ] column_alias ] + [, expression [ [ AS ] column_alias ] ]*; +``` + +Where: + +- `expression`: the expression to be evaluated. It can be a constant, a mathematical function, a string function, a date-time function, or an aggregate function. Currently, only functions that take **no arguments or constant arguments only** are supported. + +- `column_alias`: an optional alias for the result column, which improves the readability of query results. If no alias is specified, the system automatically generates column names such as `_col0`, `_col1`, etc. + +- `SELECT *` is not supported. + +- When executing `SELECT COUNT(*);`, the result is always `1`. + +## 3. Examples + +### 3.1 Constants and Mathematical Calculations + +Query statement: + +```sql +SELECT 100 + 50 AS sum_result, + 10 * 5 AS product, + SQRT(144) AS square_root, + ABS(-25) AS absolute_value, + SIN(1) AS sin_value; +``` + +Result: + +```text ++----------+-------+-----------+--------------+------------------+ +|sum_result|product|square_root|absolute_value| sin_value| ++----------+-------+-----------+--------------+------------------+ +| 150| 50| 12.0| 25|0.8414709848078965| ++----------+-------+-----------+--------------+------------------+ +``` + +### 3.2 String Functions + +Query statement: + +```sql +SELECT + CONCAT('Hello', ' ', 'World') AS greeting, + UPPER('iotdb') AS uppercase, + LOWER('IOTDB') AS lowercase, + LENGTH('database') AS str_length; +``` + +Result: + +```text ++-----------+---------+---------+----------+ +| greeting|uppercase|lowercase|str_length| ++-----------+---------+---------+----------+ +|Hello World| IOTDB| iotdb| 8| ++-----------+---------+---------+----------+ +``` + +### 3.3 Date and Time Functions + +Query statement: + +```sql +SELECT NOW() AS now_time; +``` + +Result: + +```text ++-------------+ +| now_time| ++-------------+ +|1784776724555| ++-------------+ +``` + +### 3.4 Aggregate Functions + +Query statement: + +```sql +SELECT + AVG(10), + SUM(10), + COUNT(10), + COUNT(*); +``` + +Result: + +```text ++-----+-----+-----+-----+ +|_col0|_col1|_col2|_col3| ++-----+-----+-----+-----+ +| 10.0| 10.0| 1| 1| ++-----+-----+-----+-----+ +``` diff --git a/src/zh/UserGuide/Master/Table/SQL-Manual/Tableless-Query_apache.md b/src/zh/UserGuide/Master/Table/SQL-Manual/Tableless-Query_apache.md new file mode 100644 index 000000000..b412fea24 --- /dev/null +++ b/src/zh/UserGuide/Master/Table/SQL-Manual/Tableless-Query_apache.md @@ -0,0 +1,131 @@ + + +# 无表查询 + +## 1. 功能概述 + +无表查询支持在不依赖实际数据库表的情况下,直接执行不包含 `FROM` 子句的 SQL 查询语句,获取计算结果、常量值或系统信息,主要用于表达式计算、系统函数调用、常量查询等场景。 + +> 注意:自 V2.0.11 版本起支持该功能。 + +## 2. 语法定义 + +```sql +SELECT expression [ [ AS ] column_alias ] + [, expression [ [ AS ] column_alias ] ]*; +``` + +其中: + +- `expression`:待计算的表达式,可以是常量、数学函数、字符串函数、日期时间函数、聚合函数,目前支持**无参数或只需传入常量参数**的函数。 + +- `column_alias`:可选的结果列别名,用于提升查询结果的可读性。未指定别名时,系统会自动生成 `_col0`、`_col1` 等列名。 + +- 不支持使用 `SELECT *`。 + +- 执行 `SELECT COUNT(*);` 时,结果始终为 `1`。 + +## 3. 使用示例 + +### 3.1 常量与数学计算 + +查询语句: + +```sql +SELECT 100 + 50 AS sum_result, + 10 * 5 AS product, + SQRT(144) AS square_root, + ABS(-25) AS absolute_value, + SIN(1) AS sin_value; +``` + +返回结果: + +```text ++----------+-------+-----------+--------------+------------------+ +|sum_result|product|square_root|absolute_value| sin_value| ++----------+-------+-----------+--------------+------------------+ +| 150| 50| 12.0| 25|0.8414709848078965| ++----------+-------+-----------+--------------+------------------+ +``` + +### 3.2 字符串函数 + +查询语句: + +```sql +SELECT + CONCAT('Hello', ' ', 'World') AS greeting, + UPPER('iotdb') AS uppercase, + LOWER('IOTDB') AS lowercase, + LENGTH('database') AS str_length; +``` + +返回结果: + +```text ++-----------+---------+---------+----------+ +| greeting|uppercase|lowercase|str_length| ++-----------+---------+---------+----------+ +|Hello World| IOTDB| iotdb| 8| ++-----------+---------+---------+----------+ +``` + +### 3.3 日期时间函数 + +查询语句: + +```sql +SELECT NOW() AS now_time; +``` + +返回结果: + +```text ++-------------+ +| now_time| ++-------------+ +|1784776724555| ++-------------+ +``` + +### 3.4 聚合函数 + +查询语句: + +```sql +SELECT + AVG(10), + SUM(10), + COUNT(10), + COUNT(*); +``` + +返回结果: + +```text ++-----+-----+-----+-----+ +|_col0|_col1|_col2|_col3| ++-----+-----+-----+-----+ +| 10.0| 10.0| 1| 1| ++-----+-----+-----+-----+ +``` diff --git a/src/zh/UserGuide/latest-Table/SQL-Manual/Tableless-Query_apache.md b/src/zh/UserGuide/latest-Table/SQL-Manual/Tableless-Query_apache.md new file mode 100644 index 000000000..b412fea24 --- /dev/null +++ b/src/zh/UserGuide/latest-Table/SQL-Manual/Tableless-Query_apache.md @@ -0,0 +1,131 @@ + + +# 无表查询 + +## 1. 功能概述 + +无表查询支持在不依赖实际数据库表的情况下,直接执行不包含 `FROM` 子句的 SQL 查询语句,获取计算结果、常量值或系统信息,主要用于表达式计算、系统函数调用、常量查询等场景。 + +> 注意:自 V2.0.11 版本起支持该功能。 + +## 2. 语法定义 + +```sql +SELECT expression [ [ AS ] column_alias ] + [, expression [ [ AS ] column_alias ] ]*; +``` + +其中: + +- `expression`:待计算的表达式,可以是常量、数学函数、字符串函数、日期时间函数、聚合函数,目前支持**无参数或只需传入常量参数**的函数。 + +- `column_alias`:可选的结果列别名,用于提升查询结果的可读性。未指定别名时,系统会自动生成 `_col0`、`_col1` 等列名。 + +- 不支持使用 `SELECT *`。 + +- 执行 `SELECT COUNT(*);` 时,结果始终为 `1`。 + +## 3. 使用示例 + +### 3.1 常量与数学计算 + +查询语句: + +```sql +SELECT 100 + 50 AS sum_result, + 10 * 5 AS product, + SQRT(144) AS square_root, + ABS(-25) AS absolute_value, + SIN(1) AS sin_value; +``` + +返回结果: + +```text ++----------+-------+-----------+--------------+------------------+ +|sum_result|product|square_root|absolute_value| sin_value| ++----------+-------+-----------+--------------+------------------+ +| 150| 50| 12.0| 25|0.8414709848078965| ++----------+-------+-----------+--------------+------------------+ +``` + +### 3.2 字符串函数 + +查询语句: + +```sql +SELECT + CONCAT('Hello', ' ', 'World') AS greeting, + UPPER('iotdb') AS uppercase, + LOWER('IOTDB') AS lowercase, + LENGTH('database') AS str_length; +``` + +返回结果: + +```text ++-----------+---------+---------+----------+ +| greeting|uppercase|lowercase|str_length| ++-----------+---------+---------+----------+ +|Hello World| IOTDB| iotdb| 8| ++-----------+---------+---------+----------+ +``` + +### 3.3 日期时间函数 + +查询语句: + +```sql +SELECT NOW() AS now_time; +``` + +返回结果: + +```text ++-------------+ +| now_time| ++-------------+ +|1784776724555| ++-------------+ +``` + +### 3.4 聚合函数 + +查询语句: + +```sql +SELECT + AVG(10), + SUM(10), + COUNT(10), + COUNT(*); +``` + +返回结果: + +```text ++-----+-----+-----+-----+ +|_col0|_col1|_col2|_col3| ++-----+-----+-----+-----+ +| 10.0| 10.0| 1| 1| ++-----+-----+-----+-----+ +```