Mysql 变量&分支

Posted 2020-11-10 supper李狗嗨

SELECT
    CASE 3 
        WHEN 1 THEN    ‘one‘ 
        WHEN 2 THEN    ‘two‘ 
    ELSE ‘more‘ END;

SELECT
    CASE WHEN 1 > 0 THEN ‘true‘ ELSE ‘false‘ END AS ‘one‘,
    CASE WHEN 0 > 0 THEN ‘true‘ ELSE ‘false‘ END AS ‘two‘;

SELECT 
    CASE BINARY ‘BB‘
        WHEN ‘a‘ THEN 1 
        WHEN ‘bb‘ THEN 2 
    END; 

SELECT 
    CASE ‘B‘
        WHEN ‘a‘ THEN 1 
        WHEN ‘b‘ THEN 2 
    END; 

SELECT IF(1>2,2,3);

select STRCMP(‘text2‘, ‘text‘); 

这里要使用变量来保存数据，直接使用@变量

SET @cq:=(SELECT A.id FROM emis.view1 A WHERE id = 6);
SELECT @cq AS ‘变量声明赋值的方法‘;

SET @c=(SELECT A.printer_addr FROM emis.view1 A WHERE id = @cq);
SELECT @c AS ‘变量声明赋值的方法 @cq 查找‘;


注意上面两种赋值符号，使用set时可以用“=”或“：=”，但是使用select时必须用“：=赋值” 
SELECT @bb:=id FROM emis.view1 A WHERE id = @cq;

SELECT @bb;