Question

我有以下SQL在psql中可以正常工作：

SELECT
   parent.relname, child.relname       AS child
FROM pg_inherits
    JOIN pg_class parent            ON pg_inherits.inhparent = parent.oid
    JOIN pg_class child             ON pg_inherits.inhrelid   = child.oid
    JOIN pg_namespace nmsp_parent   ON nmsp_parent.oid  = parent.relnamespace
    JOIN pg_namespace nmsp_child    ON nmsp_child.oid   = child.relnamespace
WHERE parent.relname='table_name';

问题是，当我将其放在创建功能块中时：

CREATE OR REPLACE FUNCTION my_function(tablename text)
RETURNS SETOF RECORD AS
$$


  SELECT
   parent.relname, child.relname       AS child
FROM pg_inherits
    JOIN pg_class parent            ON pg_inherits.inhparent = parent.oid
    JOIN pg_class child             ON pg_inherits.inhrelid   = child.oid
    JOIN pg_namespace nmsp_parent   ON nmsp_parent.oid  = parent.relnamespace
    JOIN pg_namespace nmsp_child    ON nmsp_child.oid   = child.relnamespace
WHERE parent.relname= tablename;



$$ LANGUAGE plpgsql;

我遇到错误：

ERROR:  schema "parent" does not exist
LINE 10:     parent.relname

，

当我尝试“ public.parent.relname”时，出现的错误是：

ERROR:  cross-database references are not implemented: 

    public.parent.relname
    LINE 10:     public.parent.relname

我该如何正确处理这种情况，我的语法有什么问题？

Answer 1

在您提供的示例中，我看到了几个错误。我以您的示例为例，突然出现了几件事：

未声明返回类型（可以是记录，表，自定义类型...）
未声明语言名称（plpgsql，sql，c，...）
...

看看documentation，您可以找到有关如何在PostgreSQL中创建函数的更多信息，并且还有很多示例（谷歌，stackoverflow，博客文章）。

根据您的示例（也取决于返回类型，语言名称）为我工作的示例：

CREATE OR REPLACE FUNCTION my_function()
RETURNS SETOF RECORD AS 
$$ 
SELECT
    parent.relname, child.relname       AS child
FROM pg_inherits
    JOIN pg_class parent            ON pg_inherits.inhparent = parent.oid
    JOIN pg_class child             ON pg_inherits.inhrelid   = child.oid
    JOIN pg_namespace nmsp_parent   ON nmsp_parent.oid  = parent.relnamespace
    JOIN pg_namespace nmsp_child    ON nmsp_child.oid   = child.relnamespace
WHERE parent.relname='table_name';
$$ LANGUAGE sql;

Answer 2

这对我有用：

CREATE OR REPLACE FUNCTION my_function (tablename text)
RETURNS TEXT AS
$$
DECLARE
  ret text := '';

BEGIN

SELECT
    parent.relname, child.relname

FROM pg_inherits
    JOIN pg_class parent            ON pg_inherits.inhparent = parent.oid
    JOIN pg_class child             ON pg_inherits.inhrelid   = child.oid
    JOIN pg_namespace nmsp_parent   ON nmsp_parent.oid  = parent.relnamespace
    JOIN pg_namespace nmsp_child    ON nmsp_child.oid   = child.relnamespace
WHERE parent.relname= tablename;



RETURN ret;


END;


$$ LANGUAGE plpgsql;

由于语言必须为“ plpgsql”，因此必须使用BEGIN / END块

Postgres用户定义的函数：SQL中的自联接

2 个答案: