add if in table basic function from 2091

src/UserGuide/Master/Table/SQL-Manual/Basis-Function_apache.md

@@ -1286,6 +1286,50 @@ Returns the first non-null value from the given list of parameters.
 coalesce(value1, value2[, ...])
 ```
 
+### 7.3 IF Expression
+The IF expression has two forms: one that specifies only the true value, and another that specifies both the true value and the false value.
+
+| Form                                         | Description                                                                                                                          | Output Type Restrictions |
+| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
+| `IF(condition, true_value)`              | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `null` is returned and `true_value` is not evaluated. | — |
+| `IF(condition, true_value, false_value)` | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `false_value` is computed and returned. | The data types of `true_value` and `false_value` **must be exactly the same**. Implicit type conversion is not supported. |
+
+> Supported since V2.0.9-beta
+
+**Examples:**
+
+1. Equivalent examples of IF and CASE expressions:
+```SQL
+-- IF syntax
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- Equivalent CASE syntax
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. Output type restriction examples:
+```SQL
+-- Succeeds
+-- temperature (float) and humidity (float) have matching types
+SELECT IF(temperature > 85, temperature, humidity) FROM table1;
+
+-- Fails
+-- temperature (float) and status (boolean) have mismatched types
+SELECT IF(temperature > 85, temperature, status) FROM table1;
+```
+
+
 ## 8. Conversion Functions
 
 ### 8.1 Conversion Functions

src/UserGuide/Master/Table/SQL-Manual/Basis-Function_timecho.md

@@ -1287,6 +1287,51 @@ Returns the first non-null value from the given list of parameters.
 coalesce(value1, value2[, ...])
 ```
 
+### 7.3 IF Expression
+
+The IF expression has two forms: one that specifies only the true value, and another that specifies both the true value and the false value.
+
+| Form                                         | Description                                                                                                                          | Output Type Restrictions |
+| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
+| `IF(condition, true_value)`              | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `null` is returned and `true_value` is not evaluated. | — |
+| `IF(condition, true_value, false_value)` | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `false_value` is computed and returned. | The data types of `true_value` and `false_value` **must be exactly the same**. Implicit type conversion is not supported. |
+
+> Supported since V2.0.9.1
+
+**Examples:**
+
+1. Equivalent examples of IF and CASE expressions:
+```SQL
+-- IF syntax
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- Equivalent CASE syntax
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. Output type restriction examples:
+```SQL
+-- Succeeds
+-- temperature (float) and humidity (float) have matching types
+SELECT IF(temperature > 85, temperature, humidity) FROM table1;
+
+-- Fails
+-- temperature (float) and status (boolean) have mismatched types
+SELECT IF(temperature > 85, temperature, status) FROM table1;
+```
+
+
 ## 8. Conversion Functions
 
 ### 8.1 Conversion Functions

src/UserGuide/latest-Table/SQL-Manual/Basis-Function_apache.md

@@ -1286,6 +1286,50 @@ Returns the first non-null value from the given list of parameters.
 coalesce(value1, value2[, ...])
 ```
 
+### 7.3 IF Expression
+The IF expression has two forms: one that specifies only the true value, and another that specifies both the true value and the false value.
+
+| Form                                         | Description                                                                                                                          | Output Type Restrictions |
+| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
+| `IF(condition, true_value)`              | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `null` is returned and `true_value` is not evaluated. | — |
+| `IF(condition, true_value, false_value)` | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `false_value` is computed and returned. | The data types of `true_value` and `false_value` **must be exactly the same**. Implicit type conversion is not supported. |
+
+> Supported since V2.0.9-beta
+
+**Examples:**
+
+1. Equivalent examples of IF and CASE expressions:
+```SQL
+-- IF syntax
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- Equivalent CASE syntax
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. Output type restriction examples:
+```SQL
+-- Succeeds
+-- temperature (float) and humidity (float) have matching types
+SELECT IF(temperature > 85, temperature, humidity) FROM table1;
+
+-- Fails
+-- temperature (float) and status (boolean) have mismatched types
+SELECT IF(temperature > 85, temperature, status) FROM table1;
+```
+
+
 ## 8. Conversion Functions
 
 ### 8.1 Conversion Functions

src/UserGuide/latest-Table/SQL-Manual/Basis-Function_timecho.md

@@ -1287,6 +1287,51 @@ Returns the first non-null value from the given list of parameters.
 coalesce(value1, value2[, ...])
 ```
 
+### 7.3 IF Expression
+
+The IF expression has two forms: one that specifies only the true value, and another that specifies both the true value and the false value.
+
+| Form                                         | Description                                                                                                                          | Output Type Restrictions |
+| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
+| `IF(condition, true_value)`              | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `null` is returned and `true_value` is not evaluated. | — |
+| `IF(condition, true_value, false_value)` | If the condition evaluates to true, `true_value` is computed and returned; otherwise, `false_value` is computed and returned. | The data types of `true_value` and `false_value` **must be exactly the same**. Implicit type conversion is not supported. |
+
+> Supported since V2.0.9.1
+
+**Examples:**
+
+1. Equivalent examples of IF and CASE expressions:
+```SQL
+-- IF syntax
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- Equivalent CASE syntax
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. Output type restriction examples:
+```SQL
+-- Succeeds
+-- temperature (float) and humidity (float) have matching types
+SELECT IF(temperature > 85, temperature, humidity) FROM table1;
+
+-- Fails
+-- temperature (float) and status (boolean) have mismatched types
+SELECT IF(temperature > 85, temperature, status) FROM table1;
+```
+
+
 ## 8. Conversion Functions
 
 ### 8.1 Conversion Functions

src/zh/UserGuide/Master/Table/SQL-Manual/Basis-Function_apache.md

@@ -1265,14 +1265,61 @@ SELECT a, b,
 coalesce(value1, value2[, ...])
 ```
 
+### 7.3 IF 表达式
+
+IF 表达式有两种形式：一种仅指定真值（true\_value），另一种同时指定真值和假值（false\_value）。
+
+| 形式                                         | 说明                                                                                                      | 输出类型限制                                                                                  |
+| ---------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
+| `if(condition, true_value)`              | 若条件（condition）为真，则计算并返回`true_value`；否则返回`null`，且`true_value`不会被计算。 |                                                                                               |
+| `if(condition, true_value, false_value)` | 若条件（condition）为真，则计算并返回`true_value`；否则计算并返回`false_value`。                  | `true_value`和`false_value`的数据类型​**必须完全一致**​，不支持隐式类型转换。 |
+
+> V 2.0.9-beta 版本起支持
+
+**示例：**
+
+1. IF 表达式和 CASE 表达式等价示例：
+
+```SQL
+-- IF 写法
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- CASE 等价写法
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. 输出类型限制示例：
+
+```SQL
+-- 成功
+-- temperature（float) 和 humidity（float） 类型一致
+select if(temperature > 85, temperature, humidity) from table1 
+
+-- 失败
+-- temperature(float) 和 status(boolean) 类型不一致
+select if(temperature > 85, temperature, status) from table1  
+```
+
+
 ## 8. 转换函数
 
 ### 8.1 转换函数
 
 #### 8.1.1 cast(value AS type) → type
 
 1. 显式地将一个值转换为指定类型。
-2. 可以用于将字符串（varchar）转换为数值类型，或数值转换为字符串类型。
+2. 可以用于将字符串（varchar）转换为数值类型，或数值转换为字符串类型
 3. 如果转换失败，将抛出运行时错误。
 
 示例：

src/zh/UserGuide/Master/Table/SQL-Manual/Basis-Function_timecho.md

@@ -1265,6 +1265,55 @@ SELECT a, b,
 coalesce(value1, value2[, ...])
 ```
 
+
+### 7.3 IF 表达式
+
+IF 表达式有两种形式：一种仅指定真值（true\_value），另一种同时指定真值和假值（false\_value）。
+
+| 形式                                         | 说明                                                                                                      | 输出类型限制                                                                                  |
+| ---------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
+| `if(condition, true_value)`              | 若条件（condition）为真，则计算并返回`true_value`；否则返回`null`，且`true_value`不会被计算。 |                                                                                               |
+| `if(condition, true_value, false_value)` | 若条件（condition）为真，则计算并返回`true_value`；否则计算并返回`false_value`。                  | `true_value`和`false_value`的数据类型​**必须完全一致**​，不支持隐式类型转换。 |
+
+> V 2.0.9.1 版本起支持
+
+**示例：**
+
+1. IF 表达式和 CASE 表达式等价示例：
+
+```SQL
+-- IF 写法
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- CASE 等价写法
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. 输出类型限制示例：
+
+```SQL
+-- 成功
+-- temperature（float) 和 humidity（float） 类型一致
+select if(temperature > 85, temperature, humidity) from table1 
+
+-- 失败
+-- temperature(float) 和 status(boolean) 类型不一致
+select if(temperature > 85, temperature, status) from table1  
+```
+
+
+
 ## 8. 转换函数
 
 ### 8.1 转换函数

src/zh/UserGuide/latest-Table/SQL-Manual/Basis-Function_apache.md

@@ -1265,6 +1265,53 @@ SELECT a, b,
 coalesce(value1, value2[, ...])
 ```
 
+### 7.3 IF 表达式
+
+IF 表达式有两种形式：一种仅指定真值（true\_value），另一种同时指定真值和假值（false\_value）。
+
+| 形式                                         | 说明                                                                                                      | 输出类型限制                                                                                  |
+| ---------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
+| `if(condition, true_value)`              | 若条件（condition）为真，则计算并返回`true_value`；否则返回`null`，且`true_value`不会被计算。 |                                                                                               |
+| `if(condition, true_value, false_value)` | 若条件（condition）为真，则计算并返回`true_value`；否则计算并返回`false_value`。                  | `true_value`和`false_value`的数据类型​**必须完全一致**​，不支持隐式类型转换。 |
+
+> V2.0.9-beta 版本起支持
+
+**示例：**
+
+1. IF 表达式和 CASE 表达式等价示例：
+
+```SQL
+-- IF 写法
+SELECT 
+  device_id,
+  temperature,  
+  IF(temperature > 85, 'High Value', 'Low Value')
+FROM table1;
+
+-- CASE 等价写法
+SELECT
+  device_id,  
+  temperature,  
+  CASE    
+    WHEN temperature > 85 THEN 'High Value'
+    ELSE 'Low Value'  
+  END
+FROM table1;
+```
+
+2. 输出类型限制示例：
+
+```SQL
+-- 成功
+-- temperature（float) 和 humidity（float） 类型一致
+select if(temperature > 85, temperature, humidity) from table1 
+
+-- 失败
+-- temperature(float) 和 status(boolean) 类型不一致
+select if(temperature > 85, temperature, status) from table1  
+```
+
+
 ## 8. 转换函数
 
 ### 8.1 转换函数