SQL条件

Question

我有这个sql：

Select 
    t1.field01, 
    t1.field02, 
    t2.name02, 
    t2.surname02, 
from 
    lib01/FirstFile as t1, 
    lib02/SecondFile (lib02/ThirdFile) as t2 
where 
    t1.field01 = t2.field02 (or t3.filed02)

我需要条件if t1.field02 is equal to "AX"我必须读取第二个文件（lib02 / SecondFile），if t1.field02 is equal to "BX"我必须阅读第三个文件（lib02 / ThirdFile）。

Answer 1

Select      
    CASE 
       WHEN ((Select t1.field02 from lib01/FirstFile as t1 ) = AX)
           THEN Select t2.name02, t2.surname02 
                from lib02/SecondFile (lib02/ThirdFile) as t2 
    CASE 
       WHEN ((Select t1.field02 from lib01/FirstFile as t1 ) = BX)
          THEN Select t3.name02, t3.surname02 
               from (lib02/ThirdFile) as t3
    END

如果检索不是您想要的，那么在每个THEN子句之后更改代码，但这就是逻辑。

尽量避免使用join

的旧语法