如何在 SQL SELECT 语句中使用包常量?
如何在 Oracle 的简单 SELECT 查询语句中使用包变量?
How can I use a package variable in a simple SELECT query statement in Oracle?
类似
SELECT * FROM MyTable WHERE TypeId = MyPackage.MY_TYPE
是否有可能或仅在使用 PL/SQL 时(在 BEGIN/END 中使用 SELECT)?
Is it possible at all or only when using PL/SQL (use SELECT within BEGIN/END)?
推荐答案
你不能.
对于要在 SQL 语句中使用的公共包变量，您必须编写一个包装函数以将值公开给外界:
For a public package variable to be used in a SQL statement, you have to write a wrapper function to expose the value to the outside world:
SQL> create package my_constants_pkg
2 as
3 max_number constant number(2) := 42;
4 end my_constants_pkg;
5 /
Package created.
SQL> with t as
2 ( select 10 x from dual union all
3 select 50 from dual
4 )
5 select x
6 from t
7 where x < my_constants_pkg.max_number
8 /
where x < my_constants_pkg.max_number
*
ERROR at line 7:
ORA-06553: PLS-221: 'MAX_NUMBER' is not a procedure or is undefined
创建一个包装函数:
SQL> create or replace package my_constants_pkg
2 as
3 function max_number return number;
4 end my_constants_pkg;
5 /
Package created.
SQL> create package body my_constants_pkg
2 as
3 cn_max_number constant number(2) := 42
4 ;
5 function max_number return number
6 is
7 begin
8 return cn_max_number;
9 end max_number
10 ;
11 end my_constants_pkg;
12 /
Package body created.
现在它可以工作了:
SQL> with t as
2 ( select 10 x from dual union all
3 select 50 from dual
4 )
5 select x
6 from t
7 where x < my_constants_pkg.max_number()
8 /
X
----------
10
1 row selected.
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