????3????JOIN??????SELECT?????
?????????????SQL?????????????????????????????Σ?SQL??????????????JOIN?????SELECT??????????SQL standard 1992 ????????????
6.3 <table reference>
<table reference> ::=
<table name> [ [ AS ] <correlation name>
[ <left paren> <derived column list> <right paren> ] ]
| <derived table> [ AS ] <correlation name>
[ <left paren> <derived column list> <right paren> ]
| <joined table>
7.4 <from clause>
<from clause> ::=
FROM <table reference> [ { <comma> <table reference> }... ]
7.5 <joined table>
<joined table> ::=
<cross join>
| <qualified join>
| <left paren> <joined table> <right paren>
<cross join> ::=
<table reference> CROSS JOIN <table reference>
<qualified join> ::=
<table reference> [ NATURAL ] [ <join type> ] JOIN
<table reference> [ <join specification> ]
??????????????????????????????????????涼??????????????????????????????????Ч??д??SQL??????SELECT … FROM???????“??”??????????????????
??????????????table references???????????Щ?????????????????????????????table references??????INSERT??UPDATE??DELETE??MERGE??????Oracle?????????????????δ???????μ??????
?????????????
???????????????????????FROM????????????????table references?????????д??JOIN???????????JOIN?????????????????????????
????SELECT c.first_name?? c.last_name?? o.amount
????FROMcustomer_view c
????JOIN order_view o
????ON c.cust_id = o.cust_id
????4?????ANSI 92???????????
?????? ??????????????????????????????????????????????????????????????????????????????ANSI 92?????????????м??????????JOIN…ON??????WHERE???????????ν???????????????????????????????????????? ???ж???????ж?????WHERE????????????ε??????????????????????
????SELECT c.first_name?? c.last_name?? o.amount
????FROM  customer_view c??
????order_view o
????WHERE  o.amount > 100
????AND    c.cust_id = o.cust_id
????AND    c.language = 'en'
???????????joinν???????????????????????????????????????????????????????Oracle???+?????????????
?????????????
??????????ANSI 92?????JOIN????????JOINν????WHERE????С???ANSI 92???????JOIN????а??????
????5?????LIKE?ж??????ESCAPE
????SQL standard 1992 ???like?ж???????￡?
????8.5 <like predicate>
????<like predicate> ::=
????<match value> [ NOT ] LIKE <pattern>
????[ ESCAPE <escape character> ]
??????????????????SQL??????в????????????????ESCAPE???????????????к??а????%??????????????????????_?????????????
????SELECT *
????FROM  t
????WHERE  t.x LIKE 'some!_prefix%' ESCAPE '!'
?????????????
???????LIKE?ж????????ú????ESCAPE