????1????ó????У???????????????????????????????????????????????????????????????????????????С???????????????????縺????????????????????????????????ε????????????????????SQL????????????????????????????У??????????????????????????????????????SELECT * FROM T1?????????????????磺SELECT COL1??COL2 FROM T1?????????????????????????????????磺SELECT TOP 300
????COL1??COL2??COL3 FROM T1??????Щ?????????????????????????????????????????????α??α????????????????????ó???????????SQL??????????????????????????????????????
????2????????ò???????????????????float??int??char??varchar??binary??varbinary???????????????????????????????????????Щ??????????е??????????????:
????SELECT name FROM employee WHERE salary ?? 60000
??????????????У???salary?????money?????????????????????????????60000???????????????????????????????????????????????????????????
????3????????????WHERE????ж???ν??к?????????????????????????????????????????????衣?磺
????SELECT * FROM T1 WHERE F1/2=100
????????:
????SELECT * FROM T1 WHERE F1=100*2
????SELECT * FROM RECORD WHERE SUBSTRING??CARD_NO??1??4??=’5378’
????????:
????SELECT * FROM RECORD WHERE CARD_NO LIKE ‘5378??’
????SELECT member_number?? first_name?? last_name FROM members
????WHERE DATEDIFF??yy??datofbirth??GETDATE?????? > 21
????????:
????SELECT member_number?? first_name?? last_name FROM members
????WHERE dateofbirth < DATEADD??yy??-21??GETDATE??????
?????????κζ??е???????????±???裬?????????????????????????????????????????????????????
????4?????????!=??????IS NULL??IS NOT NULL??IN ??NOT IN???????????????????????????????????????????????????е?????????磺
????SELECT id FROM employee WHERE id != ""B??""
????????????????????????????????е??????????????????????????С?
????5?????????????????Σ?????????????????????????????????????????????????????????????????????????????????洢?????????????????????????????????????????????????????????????????????????????ι????
????6?????????EXISTS??NOT EXISTS????????????
????1??SELECT SUM??T1.C1??FROM T1 WHERE??
??????SELECT COUNT??*??FROM T2 WHERE T2.C2=T1.C2>0??
????2??SELECT SUM??T1.C1?? FROM T1WHERE EXISTS??
????SELECT * FROM T2 WHERE T2.C2=T1.C2??
????????????????????????????Ч??????????????????????????????????????????????????衣
???????????У????????????????????????count??*??????Ч????????????????????????????EXISTS???檔?磺
????IF ??SELECT COUNT??*?? FROM table_name WHERE column_name = ""xxx""??
????????д???
????IF EXISTS ??SELECT * FROM table_name WHERE column_name = ""xxx""??