SELECT语句的if-else条件

Question

我想修改SQL语句现在我想改变它像

SELECT id 
FROM page 
WHERE name = "Test" 
AND if idLanguage != idlanguage then idParent = idpage 

这就好比

SELECT id 
FROM page 
WHERE name = "Test" 

很简单会出现什么更好的办法做到这个？

谢谢

Answer 1

SELECT id 
FROM page 
WHERE name = "Test" 
AND (idLanguage = idlanguage OR idParent = idpage) 

是更好，因为它是有效的SQL语法。

Answer 2

如果您实际上想要在数据库中设置idParent的值，那么在选择之前您需要一个UPDATE声明。

UPDATE page SET idParent = idpage 
WHERE name = "Test" 
    AND idLanguage != idlanguage; 

SELECT id FROM page 
WHERE name = "Test" 

Answer 3

如何使用case语句？请尝试：

SELECT id 
FROM page 
WHERE name = "Test" AND 
idParent = (CASE WHEN idLanguage <> idlanguage THEN idpage ELSE idParent END)