case when and
时间: 2023-11-04 12:05:23 浏览: 30
case when and 是 SQL 中的条件语句,用于在满足多个条件时执行不同的操作。具体语法如下:
```
SELECT column1, column2, ...
FROM table_name
WHERE (condition1 AND/OR condition2 AND/OR condition3 ...);
```
其中,condition1, condition2, condition3 等为条件表达式,可为比较运算符、逻辑运算符等组合。AND 和 OR 为逻辑运算符,表示同时满足/任意满足多个条件。
举个例子,下面的语句会查询表中 age 大于 18 并且 sex 为 'male' 的记录:
```
SELECT *
FROM table_name
WHERE age > 18 AND sex = 'male';
```
相关问题
case when and or
CASE WHEN and OR are two different logical operators in SQL.
CASE WHEN is used to evaluate a condition and return a value based on that condition. It is typically used in a SELECT statement to create a new column with custom values based on certain conditions. The syntax is as follows:
```
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
ELSE result3
END
```
For example, if we want to create a new column called "age_group" based on the age of a person, we could use the following code:
```
SELECT name, age,
CASE
WHEN age < 18 THEN 'Under 18'
WHEN age >= 18 AND age < 30 THEN '18-29'
WHEN age >= 30 AND age < 50 THEN '30-49'
ELSE '50 and over'
END AS age_group
FROM people;
```
OR is used to combine multiple conditions in a WHERE or HAVING clause. It returns true if any of the conditions are true. The syntax is as follows:
```
SELECT *
FROM table
WHERE condition1 OR condition2;
```
For example, if we want to select all the records from a table where the age is either less than 18 or greater than 65, we could use the following code:
```
SELECT *
FROM people
WHERE age < 18 OR age > 65;
```
sql case when and
SQL中的CASE WHEN语句是一种条件表达式,类似于其他编程语言中的if-else语句。它可以根据条件返回不同的值,也可以用于控制SQL语句的流程。CASE WHEN语句的基本语法是:
CASE expression
WHEN value1 THEN result1
WHEN value2 THEN result2
...
ELSE default_result
END
其中expression是要进行比较的表达式,value1、value2等是要比较的值,result1、result2等是对应的结果,default_result是当没有匹配到任何值时的默认结果。
除了基本语法外,CASE WHEN语句还可以使用AND和OR来实现更复杂的逻辑判断。例如:
CASE
WHEN condition1 AND condition2 THEN result1
WHEN condition3 OR condition4 THEN result2
ELSE default_result
END
其中condition1、condition2、condition3、condition4是要进行逻辑判断的条件,result1、result2是对应的结果,default_result是当没有匹配到任何条件时的默认结果。
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