为什么有个列无效？

SQL code

SELECT TOP 7 * FROM TBL_Info WHERE IndexTop = 1 AND NOT EXISTS    (SELECT TOP 1 * FROM TBL_Info WHERE IndexTop = 1 ORDER BY PublishTime DESC)     ORDER BY PublicTime DESC

提示PublishTime列无效。不太懂EXISTS用法，怎么改才对呢？谢谢～！

[解决办法]
TBL_Info表里有PublishTime这个列吗？
[解决办法]
那个列名是否不存在？

SQL code

SELECT TOP 7 * FROM TBL_Info WHERE IndexTop = 1 AND CHECKSUM(*) NOT IN    (SELECT TOP 1 CHECKSUM(*) FROM TBL_Info WHERE IndexTop = 1 ORDER BY PublicTime DESC)     ORDER BY PublicTime DESC