为什么有个列无效？该怎么解决

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

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