编程论坛 » SQL Server论坛 » 哪一句快一点

yxpke 发表于 2008-1-22 19:12

哪一句快一点

结果是一样的，用一个简单的例子
第一句
SELECT '姓名' AS 名称, COUNT(*) AS 合计
FROM mytable
UNION ALL
SELECT name, COUNT(*) AS aa
FROM mytable GROUP BY name

第二句
SELECT '姓名' AS 名称,  sum(aa) AS 合计
FROM (SELECT name,  COUNT(*) AS aa
        FROM mytable   GROUP BY name) AS d
UNION ALL
SELECT name,  COUNT(*) AS aa
FROM mytable GROUP BY name

purana 发表于 2008-1-22 23:30

在查询计划里看看.

chenkui 发表于 2008-1-30 13:51

都差不多啦
    数据多了才能看得出

查看完整版本: 哪一句快一点