Part1-了解 SQL CASE 语句 CASE 语句提供了在 SQL 查询中执行条件逻辑的方法。它评估一组条件并根据第一个评估为 true 的条件返回结果。 CASE语句的语法如下: 代码语言:javascript 代码运行次数:0 运行 AI代码解释 CASEWHENcondition1THENresult1WHENcondition2THENresult2...ELSEdefault_resultEND 以下是每个部分的...
在SQL查询中,WHERE条件下的CASE语句用于根据条件动态生成表达式或值。它允许根据不同的条件返回不同的结果。 CASE语句有两种形式:简单CASE表达式和搜索CASE表达式。 1. 简单CA...
cast as the declared type of the <case specification>.b) If no <search condition> in a <case...
TheELSEclause has no condition as it is executed if none of theWHENconditions are matched. For example, -- CASE condition with ELSE clause in SQLSELECTcustomer_id, first_name,CASEWHENcountry ='USA'THEN'United States of America'WHENcountry ='UK'THEN'United Kingdom'ELSE'Unknown Country'ENDASc...
它的基本语法如下:IF(condition, true_value, false_value) SQL Copy其中,condition 是一个条件表达式,如果为真则返回 true_value,否则返回 false_value。让我们来看一个示例,假设我们有一个订单表 orders,包含订单的金额和状态,我们想要在查询结果中添加一列来表示订单是否为高金额订单。
我们使用的条件表达式使用的 When 和 Case 的函数,这个其实就对应于 SQL 里的 CASE 和 WHEN 函数。 我们先来说一下需求,我们在获取 Client 数据的时候,想要知道这条数据 registered_on 日期字段所在的季节,比如 1月就是 Spring,7月就是 Autumn。
The CASE expression evaluates its conditions sequentially and stops with the first condition whose condition is satisfied. In some situations, an expression is evaluated before a CASE expression receives the results of the expression as its input. Errors in evaluating these expressions are possible. ...
The target value or expression that is returned when an expression or Boolean condition is evaluated. The data types of all the result expressions must be convertible to a single output type. condition A Boolean expression that evaluates to true or false. Ifconditionis true, the value of the ...
---流程函数在一个SQL语句中实现条件选择 模拟对职员薪水进行分类: mysql> create table salary_tab(useridintnotnullprimary key,salary dec(9,2)); Query OK,0rows affected (0.04sec) mysql> insert into salary_tab values(1,1000); mysql> insert into salary_tab values(2,2000); ...
Access Code - DELETE Statement with DISTINCTROW and T-SQL Access Now() vs. T-SQL GETDATE() ? ADD and SUBTRACT depending on the condition is CASE STATEMENT ADD COLUMN to variable table? Add prefix in data column Add Time in SQL HH:MM:SS to another HH:MM:SS Adding a column to a lar...