甲骨文AS关键字和子查询

Question

刚刚发现，当您使用AS关键字别名子查询Oracle不喜欢它：

SELECT * FROM (SELECT * FROM products) AS p 

我需要让我的SQL查询，尽可能实现可移植性。在上述查询中删除AS关键字是否会影响任何其他RDBMS？

Answer 1

为SQL 99 ANSI模式是表可以有一个别名WITHOUT的AS关键字的话，你可以拿出AS，它应该在每一个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 <表参考>，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> 

---

也确认工作：

• 的MS Access（Jet）中