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add if in table basic function from 2091 (#1090)
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Lines changed: 371 additions & 1 deletion

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

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@@ -1286,6 +1286,50 @@ Returns the first non-null value from the given list of parameters.
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coalesce(value1, value2[, ...])
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```
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### 7.3 IF Expression
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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.
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| Form | Description | Output Type Restrictions |
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| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
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| `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. | — |
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| `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. |
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> Supported since V2.0.9-beta
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**Examples:**
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1. Equivalent examples of IF and CASE expressions:
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```SQL
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-- IF syntax
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SELECT
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device_id,
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temperature,
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IF(temperature > 85, 'High Value', 'Low Value')
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FROM table1;
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-- Equivalent CASE syntax
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
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ELSE 'Low Value'
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END
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FROM table1;
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```
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2. Output type restriction examples:
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```SQL
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-- Succeeds
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-- temperature (float) and humidity (float) have matching types
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SELECT IF(temperature > 85, temperature, humidity) FROM table1;
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-- Fails
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-- temperature (float) and status (boolean) have mismatched types
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SELECT IF(temperature > 85, temperature, status) FROM table1;
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```
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## 8. Conversion Functions
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### 8.1 Conversion Functions

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

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Original file line numberDiff line numberDiff line change
@@ -1287,6 +1287,51 @@ Returns the first non-null value from the given list of parameters.
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coalesce(value1, value2[, ...])
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```
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### 7.3 IF Expression
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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.
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| Form | Description | Output Type Restrictions |
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| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
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| `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. | — |
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| `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. |
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> Supported since V2.0.9.1
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**Examples:**
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1. Equivalent examples of IF and CASE expressions:
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```SQL
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-- IF syntax
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SELECT
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device_id,
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temperature,
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IF(temperature > 85, 'High Value', 'Low Value')
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FROM table1;
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-- Equivalent CASE syntax
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
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ELSE 'Low Value'
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END
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FROM table1;
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```
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2. Output type restriction examples:
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```SQL
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-- Succeeds
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-- temperature (float) and humidity (float) have matching types
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SELECT IF(temperature > 85, temperature, humidity) FROM table1;
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-- Fails
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-- temperature (float) and status (boolean) have mismatched types
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SELECT IF(temperature > 85, temperature, status) FROM table1;
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```
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12901335
## 8. Conversion Functions
12911336

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### 8.1 Conversion Functions

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

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Original file line numberDiff line numberDiff line change
@@ -1286,6 +1286,50 @@ Returns the first non-null value from the given list of parameters.
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coalesce(value1, value2[, ...])
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```
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### 7.3 IF Expression
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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.
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| Form | Description | Output Type Restrictions |
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| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
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| `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. | — |
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| `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. |
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> Supported since V2.0.9-beta
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**Examples:**
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1. Equivalent examples of IF and CASE expressions:
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```SQL
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-- IF syntax
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SELECT
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device_id,
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temperature,
1307+
IF(temperature > 85, 'High Value', 'Low Value')
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FROM table1;
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-- Equivalent CASE syntax
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
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ELSE 'Low Value'
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END
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FROM table1;
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```
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2. Output type restriction examples:
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```SQL
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-- Succeeds
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-- temperature (float) and humidity (float) have matching types
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SELECT IF(temperature > 85, temperature, humidity) FROM table1;
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-- Fails
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-- temperature (float) and status (boolean) have mismatched types
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SELECT IF(temperature > 85, temperature, status) FROM table1;
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```
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12891333
## 8. Conversion Functions
12901334

12911335
### 8.1 Conversion Functions

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

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Original file line numberDiff line numberDiff line change
@@ -1287,6 +1287,51 @@ Returns the first non-null value from the given list of parameters.
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coalesce(value1, value2[, ...])
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```
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### 7.3 IF Expression
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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.
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| Form | Description | Output Type Restrictions |
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| ---------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------ | ------------------------ |
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| `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. | — |
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| `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. |
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> Supported since V2.0.9.1
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**Examples:**
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1. Equivalent examples of IF and CASE expressions:
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```SQL
1305+
-- IF syntax
1306+
SELECT
1307+
device_id,
1308+
temperature,
1309+
IF(temperature > 85, 'High Value', 'Low Value')
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FROM table1;
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-- Equivalent CASE syntax
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
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ELSE 'Low Value'
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END
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FROM table1;
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```
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2. Output type restriction examples:
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```SQL
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-- Succeeds
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-- temperature (float) and humidity (float) have matching types
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SELECT IF(temperature > 85, temperature, humidity) FROM table1;
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-- Fails
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-- temperature (float) and status (boolean) have mismatched types
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SELECT IF(temperature > 85, temperature, status) FROM table1;
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```
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12901335
## 8. Conversion Functions
12911336

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### 8.1 Conversion Functions

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

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Original file line numberDiff line numberDiff line change
@@ -1265,14 +1265,61 @@ SELECT a, b,
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coalesce(value1, value2[, ...])
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```
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### 7.3 IF 表达式
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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）。
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| 形式 | 说明 | 输出类型限制 |
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| ---------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
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| `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。 | |
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| `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。 |
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> V 2.0.9-beta 版本起支持
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**示例：**
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1. IF 表达式和 CASE 表达式等价示例：
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```SQL
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-- IF 写法
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SELECT
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device_id,
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temperature,
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IF(temperature > 85, 'High Value', 'Low Value')
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FROM table1;
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-- CASE 等价写法
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
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ELSE 'Low Value'
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END
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FROM table1;
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```
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2. 输出类型限制示例：
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```SQL
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-- 成功
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-- temperature（float) 和 humidity（float） 类型一致
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select if(temperature > 85, temperature, humidity) from table1
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-- 失败
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-- temperature(float) 和 status(boolean) 类型不一致
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select if(temperature > 85, temperature, status) from table1
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```
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## 8. 转换函数
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### 8.1 转换函数
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#### 8.1.1 cast(value AS type) → type
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1. 显式地将一个值转换为指定类型。
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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。
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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
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3. 如果转换失败，将抛出运行时错误。
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示例：

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

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coalesce(value1, value2[, ...])
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```
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### 7.3 IF 表达式
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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）。
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| 形式 | 说明 | 输出类型限制 |
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| ---------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
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| `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。 | |
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| `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。 |
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> V 2.0.9.1 版本起支持
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**示例：**
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1. IF 表达式和 CASE 表达式等价示例：
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```SQL
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-- IF 写法
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SELECT
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device_id,
1288+
temperature,
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IF(temperature > 85, 'High Value', 'Low Value')
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FROM table1;
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-- CASE 等价写法
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
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ELSE 'Low Value'
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END
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FROM table1;
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```
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2. 输出类型限制示例：
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```SQL
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-- 成功
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-- temperature（float) 和 humidity（float） 类型一致
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select if(temperature > 85, temperature, humidity) from table1
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-- 失败
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-- temperature(float) 和 status(boolean) 类型不一致
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select if(temperature > 85, temperature, status) from table1
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```
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## 8. 转换函数
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### 8.1 转换函数

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

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Original file line numberDiff line numberDiff line change
@@ -1265,6 +1265,53 @@ SELECT a, b,
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coalesce(value1, value2[, ...])
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```
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### 7.3 IF 表达式
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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）。
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| 形式 | 说明 | 输出类型限制 |
1273+
| ---------------------------------------------- | ----------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------- |
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| `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。 | |
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| `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。 |
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> V2.0.9-beta 版本起支持
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**示例：**
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1. IF 表达式和 CASE 表达式等价示例：
1282+
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```SQL
1284+
-- IF 写法
1285+
SELECT
1286+
device_id,
1287+
temperature,
1288+
IF(temperature > 85, 'High Value', 'Low Value')
1289+
FROM table1;
1290+
1291+
-- CASE 等价写法
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SELECT
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device_id,
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temperature,
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CASE
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WHEN temperature > 85 THEN 'High Value'
1297+
ELSE 'Low Value'
1298+
END
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FROM table1;
1300+
```
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2. 输出类型限制示例：
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1304+
```SQL
1305+
-- 成功
1306+
-- temperature（float) 和 humidity（float） 类型一致
1307+
select if(temperature > 85, temperature, humidity) from table1
1308+
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-- 失败
1310+
-- temperature(float) 和 status(boolean) 类型不一致
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select if(temperature > 85, temperature, status) from table1
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```
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## 8. 转换函数
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12701317
### 8.1 转换函数

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