CASE WHEN 在語句中不同位置的用法
1、SELECT?CASE WHEN 用法
SELECT???grade,?COUNT?(CASE?WHEN?sex?=?1?THEN?1??????/*sex?1為男生，2位女生*/ ???????????????????????ELSE?NULL ???????????????????????END)?男生數, ????????????????COUNT?(CASE?WHEN?sex?=?2?THEN?1 ???????????????????????ELSE?NULL ???????????????????????END)?女生數 ????FROM?students?GROUP?BY?grade;
2、WHERE?CASE WHEN 用法
SELECT?T2.*,?T1.* ???FROM?T1,?T2 ??WHERE?(CASE?WHEN?T2.COMPARE_TYPE?=?'A'?AND ???????????????????T1.SOME_TYPE?LIKE?'NOTHING%' ????????????????THEN?1 ??????????????WHEN?T2.COMPARE_TYPE?!=?'A'?AND ???????????????????T1.SOME_TYPE?NOT?LIKE?'NOTHING%' ????????????????THEN?1 ??????????????ELSE?0 ???????????END)?=?1
3、group by?case when 用法
SELECT?? CASE?WHEN?salary??500?AND?salary??600?AND?salary??800?AND?salary??500?AND?salary??600?AND?salary??800?AND?salary?<p>推薦教程：<a href="https://www.php.cn/mysql-tutorials.html" target="_blank">mysql教程</a></p>
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