oracle 12c使用子查詢保理子句與plsql聲明

Question

我是子查詢保理子句的忠實粉絲。

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

和Oracle 12c中現在包括在WITH子句的PL/SQL聲明部分

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 

，但我似乎無法讓他們一起工作這可能嗎？

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; 

Answer 1

請參考語法：
https://docs.oracle.com/database/121/SQLRF/statements_10002.htm#SQLRF01702

plsql_declarations

subquery_factoring_clause

正如你看到的，語法是：

WITH [ plsql_declarations ] [ subquery_factoring_clause ] 

這意味着，PL/SQL必須先走，然後SQL查詢的休息，以這樣的方式

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;