oracle 12c 使用带有 plsql 声明的子查询因式分解子句答案

【问题标题】：oracle 12c using subquery factoring clause with plsql declarationoracle 12c 使用带有 plsql 声明的子查询因式分解子句
【发布时间】：2016-07-06 17:57:23
【问题描述】：

我是子查询分解子句的忠实粉丝。

WITH t1 as (select 1 as id from dual)
select * from t1;

oracle 12c 现在在 WITH 子句中包含一个 PL/SQL 声明部分

WITH
  FUNCTION with_function(p_id IN NUMBER) RETURN NUMBER IS
  BEGIN
    RETURN p_id;
  END;
SELECT with_function(id)
FROM   t1
WHERE  rownum = 1

但我似乎无法让他们一起工作，这可能吗？

WITH t1 as (select 1 as id from dual)
WITH  FUNCTION with_function(p_id IN NUMBER) RETURN NUMBER IS
  BEGIN
    RETURN p_id;
  END;
SELECT with_function(id)
FROM   t1
WHERE  rownum = 1;

【问题讨论】：

标签： oracle oracle12c subquery-factoring

【解决方案1】：

请参考语法：
https://docs.oracle.com/database/121/SQLRF/statements_10002.htm#SQLRF01702

plsql_declarations

subquery_factoring_clause

如您所见，语法是：

WITH [ plsql_declarations ] [ subquery_factoring_clause ]

这意味着必须先执行 PL/SQL，然后执行其余的 SQL 查询，这样：

WITH 
  FUNCTION with_function(p_id IN NUMBER) RETURN NUMBER IS
  BEGIN
    RETURN p_id;
  END;
t1 as (select 1 as id from dual)
SELECT with_function(id)
FROM   t1
WHERE  rownum = 1;

【讨论】：