甲骨文AS關鍵字和子查詢

Question

剛剛發現，當您使用AS關鍵字別名子查詢Oracle不喜歡它：

SELECT * FROM (SELECT * FROM products) AS p 

我需要讓我的SQL查詢，儘可能實現可移植性。在上述查詢中刪除AS關鍵字是否會影響任何其他RDBMS？

Answer 1

爲SQL 99 ANSI模式是表可以有一個別名WITHOUT的AS關鍵字的話，你可以拿出AS，它應該在每一個RDBMS工作。看到它在小提琴：

• MySQL
• Oracle
• PostgreSql
• SQLLite
• SQLServer

在ISO/IEC 9075-2:1999，部分7.6 <表參考>，PA GE 232：

<table reference> ::= 
    <table primary> 
    | <joined table> 

<table primary> ::= 
    <table or query name> [ [ AS ] <correlation name> 
     [ <left paren> <derived column list> <right paren> ] ] 
    | <derived table> [ AS ] <correlation name> 
     [ <left paren> <derived column list> <right paren> ] 
    | <lateral derived table> [ AS ] <correlation name> 
     [ <left paren> <derived column list> <right paren> ] 
    | <collection derived table> [ AS ] <correlation name> 
     [ <left paren> <derived column list> <right paren> ] 
    | <only spec> 
     [ [ AS ] <correlation name> 
     [ <left paren> <derived column list> <right paren> ] ] 
    | <left paren> <joined table> <right paren> 

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也確認工作：

• 的MS Access（Jet）中