你可以自己做个例子看看区别的
CREATE TABLE #Temp_1
(
NAME VARCHAR(50),
A1 INT,
A2 INT,
A3 INT
)
INSERT INTO #Temp_1
SELECT 'A',22,56,77 UNION ALL
SELECT 'B',22,55,77 UNION ALL
SELECT 'A',22,52,72 UNION ALL
SELECT 'A',24,56,77 UNION ALL
SELECT 'A',22,56,74 UNION ALL
SELECT 'A',23,56,77
SELECT * FROM #Temp_1 WHERE A2=56 OR (NAME='A' AND A1=22)
SELECT * FROM #Temp_1 WHERE A2=56 OR NAME='A' or A1=22