sql - Oracle AS 关键字和子查询

Question

刚发现Oracle不喜欢用AS关键字给子查询起别名：

SELECT * FROM (SELECT * FROM products) AS p

我需要让我的 SQL 查询尽可能可移植。删除AS上述查询中的关键字是否会影响任何其他 RDBMS？

Answer 1

SQL 99 ANSI 的模式是该表可以有一个没有关键字的别名，因此AS，您可以取出AS它，它应该适用于每个 RDBMS。在小提琴上看到它：

• MySQL
• 甲骨文
• PostgreSql
• SQLLite
• SQL服务器

在ISO/IEC 9075-2:1999的第7.6 节 <table reference>中，第 232 页：

<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：

• MS Access（喷气机）