呵呵，几乎成标题党了，今天要写个脚本查询7天内所有有登录玩家的数据，要求按注册日期统计，虽然是个简单的问题，但是关键是用户表有30个，分别是 user0, user1......到user29 ，光是把它们UNION ALL起来，我都够郁闷了，你想象下脚本有多长吧，一大堆堆在那儿，光是复制都让你难以忍受。
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->SELECT Id,CONVERT(VARCHAR(10),Create_Time, 120), Last_Login_Time FROM user0
UNION ALL
SELECT Id,CONVERT(VARCHAR(10),Create_Time, 120), Last_Login_Time FROM user1
UNION ALL
SELECT Id,CONVERT(VARCHAR(10),Create_Time, 120), Last_Login_Time FROM user2
.........
呵呵，下面是我用动态SQL 改写的，呵呵，简洁多了
Code highlighting produced by Actipro CodeHighlighter (freeware)http://www.CodeHighlighter.com/-->DECLARE @cmdText VARCHAR(8000);
DECLARE @userIndex INT;
SET @cmdText = '';
SET @userIndex = 0;
WHILE @userIndex <30
BEGIN
IF (@userIndex != 29)
SELECT @cmdText = @cmdText + 'SELECT Id,Create_Time, Last_Login_Time FROM '
+ ' dbo.user' + CONVERT(VARCHAR,@userIndex)
+ ' UNION ALL' + CHAR(10); --换行
ELSE
SELECT @cmdText = @cmdText + 'SELECT Id,Create_Time, Last_Login_Time FROM '
+ 'dbo.user' + CONVERT(VARCHAR,@userIndex) ;
SET @userIndex = @userIndex + 1;
END;
SELECT @cmdText = 'SELECT CONVERT(VARCHAR(10),T.Create_Time, 120) AS Create_Time ,COUNT(0) AS RecordNum FROM ('
+ @cmdText +
') T WHERE DATEDIFF(d,Last_Login_Time,GETDATE()) < 7 GROUP BY CONVERT(VARCHAR(10),Create_Time, 120) ';
--PRINT @cmdText
EXEC (@cmdText);