PostgreSQL。CREATE CAST '字符变化'到'整数'
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Postgresql. CREATE CAST 'character varying' to 'integer'
提问by Simon
I want to CREATE CAST a suitable function to convert 'character varying' to 'integer'. Can anyone suggest a function? Everything I try fails.
我想 CREATE CAST 一个合适的函数来将“字符变化”转换为“整数”。任何人都可以建议一个功能吗？我尝试的一切都失败了。
回答by Peter Eisentraut
Use this:
用这个：
CREATE CAST (varchar AS integer) WITH INOUT [AS IMPLICIT];
It uses the input/output functions of the data types involved.
它使用所涉及数据类型的输入/输出函数。
回答by Michael Blood
The function above works if you update your SQL to do an explicit cast. However, if you add 'as implicit' to the end of your "create cast" statement, Postgres will be able to automatically figure out what you are trying to do when you compare an integer with a varchar that can be converted to an integer.
如果您更新 SQL 以执行显式转换，则上述函数有效。但是，如果您在“create cast”语句的末尾添加“作为隐式”，当您将整数与可以转换为整数的 varchar 进行比较时，Postgres 将能够自动确定您要执行的操作。
Here is my updated statement that seemed to work "implicitly":
这是我更新的声明，似乎“隐式”起作用：
CREATE FUNCTION toint(varchar)
RETURNS integer
STRICT IMMUTABLE LANGUAGE SQL AS
'SELECT cast( as integer);';
CREATE CAST (varchar AS integer) WITH FUNCTION toint(varchar) as Implicit;
回答by Oscar Raig Colon
I got the same error. I have a COLUMN
我得到了同样的错误。我有一个列
code
代码
declared as type character varying(20) and a local variable
声明为类型字符变化（20）和局部变量
l_code
l_code
declared as type int.
声明为 int 类型。
I solved replacing in the procedure
我在程序中解决了更换
SELECT
...
WHERE
code = l_code AND
..
with
和
code = cast( l_code as character varying) AND
回答by a_horse_with_no_name
I assume you want to get back the behaviour of Postgres 8.3 regarding implicit casting.
我假设您想恢复 Postgres 8.3 关于隐式转换的行为。
See this blog entry for examples:
http://petereisentraut.blogspot.com/2008/03/readding-implicit-casts-in-postgresql.html
有关示例，请参阅此博客条目：http:
//petereisentraut.blogspot.com/2008/03/readding-implicit-casts-in-postgresql.html
Oh: and bug that vendor of the software to fix the broken SQL ;)
哦：还有那个软件供应商的 bug 来修复损坏的 SQL ;)
Edit
编辑
This should do it:
这应该这样做：
CREATE FUNCTION toint(varchar) RETURNS integer STRICT IMMUTABLE LANGUAGE SQL AS 'SELECT cast( as integer);'; CREATE CAST (varchar AS integer) WITH FUNCTION toint(varchar);
