sql中的case when 有点类似于Java中的switch语句,比较灵活,但是在Mysql中对于Null的处理有点特殊 Mysql中case when语法: 语法1: 1 2 3 4 5 CASE case_value WHEN when_value THEN statement_list [WHEN when_value THEN statement_list] ... [ELSE statement_list] END CASE 语法2: 1 2 3 4 5 CASE ...
mysql中casewhen用法 mysql中casewhen⽤法需求：需要在查询出的字段中，判断这个某个字段是否为null，并指定想要的值，SELECT temp.gId id,temp.`name`,temp.point,temp.give_user_proportion,temp.sales_price,temp.cover_img,temp.limit_num,temp.price,temp.show_sale_price,temp.isPromotion is_promotion F...
大致意思为,一个myisam引擎表在没有任何的删除,修改操作下,执行 select 不带order by,那么会按照插入顺序进行排序。 If you had done the same statement with an InnoDB table, they would have been delivered in PRIMARY KEY order, not INSERT order. Again, this is an artifact of the underlying impleme...
ApplicationofCase-wheninMySQL LIULei1,LINLi-dan2 (1.HenanPoliceCollege,Zhengzhou450000,China;2.LuoheVocationalTechnologyCollege,Luohe462000,China) Abstract:Intheactualresearchanddevelopmentwork,itisoftennecessarytowriteallkindsofSQLtostatisticallkindsofonlinebusinessdataortoperformdatafilteringoperationunderthecondit...
The following illustrates the syntax of the searched CASE statement: 1 2 3 4 5 6 CASE WHEN condition_1 THEN commands WHEN condition_2 THEN commands ... ELSE commands END CASE; MySQL evaluates each condition in the WHEN clause until it finds a condition whose value is TRUE , then corresp...
case when 用法 mysql casewhen 是一种在 MySQL 中使用的条件语句,可以在查询结果 中根据指定条件进行不同的操作。其基本语法为: CASE WHEN condition1 THEN result1 WHEN condition2 THEN result2 ... ELSE default_result END condition1、condition2 等表示条件,result1、result2 等表 示针对不同条件的操作结...
您不应在 WHEN 子句值中使用 NULL,因为如果执行,逻辑部分将为 NULL = NULL,结果为 FALSE。 现在对于 Search CASE,它遵循与 Simple CASE 相同的逻辑过程,但搜索案例的一部分使其执行起来有所不同。在这里,满足 MySQL 数据类型的值的 CASE 是基于它用于的上下文。例如,如果语句中使用了字符串上下文,则结果值将采...
The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END. For the first syntax, case_value is an expression. This value is compared to the when_value expression in each WHEN clause until one of them is equal. When an equal when_value is ...
The CASE statement cannot have an ELSE NULL clause, and it is terminated with END CASE instead of END. For the first syntax, case_value is an expression. This value is compared to the when_value expression in each WHEN clause until one of them is equal. When an equal when_value is ...
Description: When using a subquery with a case when in the update statement, the updated data does not match the expected results returned by the subquery. How to repeat: 1、prepare data: drop database if exists select_test; create database if not exists select_test; create table if not ...