sql case when

SQL中的CASE WHEN语句用于在查询结果中进行条件判断和返回不同的结果。它的基本格式为：
CASE
WHEN 条件1 THEN 结果1
WHEN 条件2 THEN 结果2
...
ELSE 默认结果
END

例如，在SELECT语句中使用CASE WHEN可以根据job_level的值返回不同的结果：
SELECT
CASE
WHEN job_level = '1' THEN '1111'
WHEN job_level = '2' THEN '1111'
WHEN job_level = '3' THEN '1111'
ELSE 'eee'
END
FROM dbo.employee

在UPDATE语句中使用CASE WHEN可以根据job_level的值更新不同的值：
UPDATE employee
SET e_wage =
CASE
WHEN job_level = '1' THEN e_wage * 1.97
WHEN job_level = '2' THEN e_wage * 1.07
WHEN job_level = '3' THEN e_wage * 1.06
ELSE e_wage * 1.05
END

相关问题

sql case when

In SQL, the `CASE WHEN` statement is used to perform conditional logic. It is used to evaluate a set of conditions and return a value based on the result of the evaluation.

The basic syntax for the `CASE WHEN` statement is as follows:

CASE 
  WHEN condition1 THEN result1
  WHEN condition2 THEN result2
  ...
  WHEN conditionN THEN resultN
  ELSE default_result
END

Here's a breakdown of what each part of the syntax does:

- `CASE` begins the `CASE WHEN` statement.
- `WHEN` specifies the condition to be evaluated.
- `THEN` specifies the value to be returned if the condition is true.
- `ELSE` specifies the value to be returned if none of the conditions are true.
- `END` ends the `CASE WHEN` statement.

Here's an example that uses `CASE WHEN` to classify products in a table based on their prices:

SELECT product_name,
       price,
       CASE
         WHEN price < 10 THEN 'Cheap'
         WHEN price >= 10 AND price < 50 THEN 'Moderate'
         WHEN price >= 50 THEN 'Expensive'
         ELSE 'Unknown'
       END AS price_category
FROM products;

In this example, the `CASE WHEN` statement evaluates the `price` column for each row in the `products` table. If the price is less than 10, it is classified as "Cheap". If the price is between 10 and 50, it is classified as "Moderate". If the price is 50 or greater, it is classified as "Expensive". If the price is not provided, it is classified as "Unknown".

Sql Case When

SQL中的CASE WHEN语句是一种条件语句，用于根据条件对数据进行条件判断和结果返回。它通常与SELECT、UPDATE或DELETE等SQL语句结合使用。

CASE WHEN语句的基本语法如下：

CASE
    WHEN condition1 THEN result1
    WHEN condition2 THEN result2
    ...
    ELSE result
END

其中，condition1、condition2等是判断条件，如果满足某个条件，则返回相应的结果。ELSE子句是可选的，用于当所有条件都不满足时的默认结果。

使用CASE WHEN语句时，可以根据不同的条件返回不同的结果，这在数据查询、更新和删除等操作中非常有用。以下是一些使用CASE WHEN语句的示例：

1. 查询符合条件的记录：

SELECT column1, column2,
    CASE
        WHEN condition1 THEN 'Condition 1'
        WHEN condition2 THEN 'Condition 2'
        ELSE 'Other'
    END AS result_column
FROM table_name;

2. 根据性别进行分组统计：

SELECT gender, COUNT(*) AS count,
    CASE
        WHEN gender = 'male' THEN 'Male'
        WHEN gender = 'female' THEN 'Female'
        ELSE 'Other'
    END AS gender_group
FROM users;

3. 根据销售额进行排名：

SELECT product_name, sales_amount,
    CASE
        WHEN sales_amount = MAX(sales_amount) THEN 'Top'
        ELSE 'Middle'
    END AS rank_column
FROM sales_table;

通过使用CASE WHEN语句，您可以根据特定的条件和需求来灵活地处理数据，并根据需要返回不同的结果。