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<HEAD><TITLE>FAQ汇萃 >> SQL之家 >> 用变量替代表名，列名的SQL命令怎样写？</title>
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>> 用变量替代表名，列名的SQL命令怎样写？ [<a href=http://www.jsp001.com/forum/showthread.php?goto=newpost&threadid=464>查看别人的评论</a>]<br>
<hr><p>由 amtd 发布于: 2001-02-15 10:00</p><p><img src="images/icons/icon1.gif" alt="Post" border=0> </p><p>用变量替代表名，列名的SQL命令怎样写？<br><br>(佚名)<br><br>答：可在帮助里查找SQL的EXEC命令信息。基本上是要运行一个已经定义好的程序。<br><br>举一个简短的例子：从一个表中选择一列<br><br>USE pubs<br><br>go<br><br><br>DECLARE @str varchar(255)<br><br>DECLARE @columnname varchar(30)<br><br><br>SELECT @columnname='au_lname'<br><br><br>SELECT @str = 'SELECT ' + @columnname + ' FROM authors'<br><br><br>EXEC (@str)<br><br>另一个例子是在线书籍中的。这个例子显示了EXECUTE命令是怎样动态处理带变量的字符串。这个例子创建一个光标（tables_cursor)来保持所有用户定义表（TYPE=‘U’）的列单。<br><br>DECLARE tables_cursor CURSOR<br><br>FOR<br><br>SELECT name FROM sysobjects WHERE type = 'U'<br><br><br>OPEN tables_cursor<br><br>DECLARE @tablename varchar(30)<br><br>FETCH NEXT FROM tables_cursor INTO @tablename<br><br>WHILE (@@fetch_status -1)<br><br>BEGIN<br><br>/*<br><br>A @@fetch_status of -2 means that the row has been deleted.<br><br>No need to test for this as the result of this loop is to<br><br>drop all user-defined tables.<br><br>*/<br><br>EXEC ("DROP TABLE " @tablename)<br><br>FETCH NEXT FROM tables_cursor INTO @tablename<br><br>END<br><br>PRINT "All user-defined tables have been dropped from the database."<br><br>DEALLOCATE tables_cursor <br><br><br>__________________<br><font color=red>真实源于生活！ </font><br>请访问我们的网站： <br>（VB爱好者乐园） <br><a href="http://www.vbgood.com" target=_blank>http://www.vbgood.com</a><br><a href="http://www.d1vb.com" target=_blank>http://www.d1vb.com</a><br><a href="http://61.128.97.225/vbgood/index.asp" target=_blank>http://61.128.97.225/vbgood/index.asp</a><br>拥有1800多个资料！ </p></td>
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