mysqlcase语句如何用?
发布时间:08/01 来源:未知 浏览:
关键词:
那么其中mysql case语句如何用?
mysql case语句用途:
构造:case when… then …end
1.推断的同时转变其值
eg:
select OperatorAccount, case when CreateTime>'2016-02-14 16:24:42' then 'after' when CreateTime<'2016-02-14 16:24:42' then 'before' else 'now' end stage from log_login order by CreateTime DESC
第二种写法
SELECT CallerNumber, CASE IsLocal WHEN 0 THEN '外线' WHEN 1 THEN '内线' END FROM cdr
2.拆分一行为多列
eg:
SELECT SipAccount, COUNT(1) AS number,IsCheck FROM cdr GROUP BY SipAccount,IsCheck
所以终究要用到行拆分成三列,语句如下
SELECT SipAccount, (CASE IsCheck WHEN 1 THEN number END) youxiu, (CASE IsCheck WHEN 2 THEN number END) hege, (CASE IsCheck WHEN 3 THEN number END) buhege FROM (SELECT SipAccount, COUNT(1) AS number,IsCheck FROM cdr GROUP BY SipAccount,IsCheck) AS a
此刻效果是这样的,你会发明虽然拆成了三列,但是终究效果还不是本人需要的,接下来就需要依据sipaccount来分组的同时对效果进行处置了。语句如下:
SELECT sipaccount, IF(MAX(youxiu) IS NULL,0, MAX(youxiu)) youxiu, IF(MAX(hege) IS NULL,0, MAX(hege)) hege, IF(MAX(buhege) IS NULL,0, MAX(buhege)) buhege FROM (SELECT SipAccount, (CASE IsCheck WHEN 1 THEN number END) youxiu, (CASE IsCheck WHEN 2 THEN number END) hege, (CASE IsCheck WHEN 3 THEN number END) buhege FROM (SELECT SipAccount, COUNT(1) AS number,IsCheck FROM cdr GROUP BY SipAccount,IsCheck) AS a) AS b GROUP BY sipaccount
终究得到了这个效果。正是我们需要的格局。
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