SQL语句AND 和 OR执行的优先级

例句：

SELECT COUNT(1) FROM RT_CUSTALLOCRESULT 
WHERE REGDATE BETWEEN '2014-03-01' AND '2014-03-31' 
OR (DATE(NEXTTRACKDATE) BETWEEN '2014-03-01' AND '2014-03-31') AND SALEID = 2003 

SELECT COUNT(1) FROM RT_CUSTALLOCRESULT 
WHERE (REGDATE BETWEEN '2014-03-01' AND '2014-03-31' 
OR (DATE(NEXTTRACKDATE) BETWEEN '2014-03-01' AND '2014-03-31')) AND SALEID = 2003 

没带括号前，优先执行

(DATE(NEXTTRACKDATE) BETWEEN '2014-03-01' AND '2014-03-31') AND SALEID = 2003 

带了括号后，优先执行

(REGDATE BETWEEN '2014-03-01' AND '2014-03-31' 
OR (DATE(NEXTTRACKDATE) BETWEEN '2014-03-01' AND '2014-03-31'))