这段SQL啥意思～～～

Question

[quote="sql
SELECT org.ID, org.orgname, org.disporder,
case when org.ID = 3 then 1
when org.ID = 4 then 2
when org.ID = 5 then 5
when org.ID = 6 then 6
when org.ID = 7 then 7
when org.ID = 8 then 8
when org.ID = 9 then 9
when org.ID = 10 then 10
when org.ID = 107 then 11
end as seq
FROM tb_org org
[/quote]
大家帮我看看，解释下。。。。。。

Answer 1

SELECT CASE '张三' WHEN '张三' THEN '张三' ELSE NULL END

-- 如果 '张三' 值是 '张三' 那么返回 '张三' 否则 返回NULL值

-- 如果(CASE) '张三' 值是(WHEN) '张三' 那么返回(THEN) '张三' 否则(ELSE) 返回NULL值 (END判断结束)

SELECT CASE '李四' WHEN '王五' THEN '李四' ELSE NULL END