sql - SELECT Statement with if-else condition

Question

I want to modify sql statement which is very simple like

SELECT id
FROM page
WHERE name = "Test"

Now I want to change it something like

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

what will the better way to do this?

Thank you

Answer 1

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

更好，因为它是有效的 SQL 语法。

Answer 2

使用case语句怎么样？请试试：

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

Answer 3

如果您真的想在数据库中设置 idParent 的值，那么您需要UPDATE在选择之前添加一条语句。

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

SELECT id FROM page
WHERE name = "Test"