基于列的逻辑表达式,其实就是CASE表达式.可以用在SELECT,UPDATE,DELETE,SET以及IN,WHERE,ORDER BY和HAVING子句之后。下面给个简单示例:
这两种方式,可以实现相同的功能。简单Case函数的写法相对比较简洁,但是和Case搜索函数相比,功能方面会有...
SQL代码如下: SELECT CASE WHEN salary <= 500 THEN '1' WHEN salary > 500 AND salary <= 600 THEN '2' WHEN salary > 600 AND salary <= 800 THEN '3' WHEN salary > 800 AND salary <= 1000 THEN '4' ELSE NULL END salary_class, -- 别名命名 COUNT(*)FROMTable_A GROUP BY CASE WHEN ...
CASE可能是 SQL 中被误用最多的关键字之一。虽然你可能以前用过这个关键字来创建字段,但是它还具有更多用法。例如,你可以在WHERE子句中使用CASE。 首先让我们看一下CASE的语法。在一般的SELECT中,其语法如下: SELECT<myColumnSpec>= CASE WHEN<A>THEN<somethingA> WHEN<B>THEN<somethingB> ELSE<somethingE> END...
SELECT country, SUM( CASE WHEN sex = '1' THEN population ELSE 0 END), --男性人口 SUM( CASE WHEN sex = '2' THEN population ELSE 0 END) --女性人口 FROM Table_A GROUP BY country; 这样我们使用Select,完成对二维表的输出形式,充分显示了Case函数的强大。
I am new to making complex (let me know if this one is not complex) SQL queries and am struggling to create a query that will join 2 tables with multiple different combinations. Here is my query for just the 1st combination. SELECTDISTINCTA.Id, A.Ref1, A.Ref2, A.Ref3, B.Ref1,...
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提示说的是这个子查询返回的是一个结果集 你这个子查询没有加条件 或者你这个子查询加一个top 1
commit;3、在表2中插入数据 insert into test_case2 values(1,'aa');insert into test_case2 values(2,'bb');insert into test_case2 values(3,'cc');insert into test_case2 values(6,'ee');commit;4、两表关联,并编写case when的语句 select t.*,case when b.id is not null ...
case when ... then .. when .. then ... end 这种表达式,是sql的不同条件分支结果。举例如下,1、创建数据表,create table test_student(stu_id number, class_id number);2、插入测试数据,insert into test_student values(1,1001);insert into test_student values(2,1001);insert into ...