请问两句SQL语句的解释
SELECT COUNT(*)
AS cnt
FROM info
WHERE CONVERT(VARCHAR,dateandtime,112)='$nowDate'
AND categoryid like '$nDirCid%'
AND n_pass=1
ORDER BY n_placetop DESC,
n_preferntial DESC,
n_nid DESC";
请问此句中AS cnt的意思
-------------------------------------------------------------------
SET ROWCOUNT 0
SET ROWCOUNT 30
SELECT n_nid,title,dateandtime,n_pass,hits,categoryid,categorytype,n_preferntial,n_placetop,n_special,n_picture,n_index
FROM info
WHERE LEFT(dateandtime,10) LIKE '$nowDate'
AND categoryid like '$nDirCid%'
AND n_pass=1
AND n_firstinfo=1
ORDER BY n_placetop DESC,
n_preferntial DESC,
n_nid $strTOT
请问此句中SET ROWCOUNT 0 SET ROWCOUNT 30 的意思