SQL查询的函数没有结果数据的目标

Question

我正在尝试创建一个返回SELECTed结果集的函数。当我调用像这个select * from tst_dates_func()的postgres函数时，我收到一个错误，如下所示：

ERROR:  query has no destination for result data
HINT:  If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT:  PL/pgSQL function "tst_dates_func" line 3 at SQL statement

********** Error **********

ERROR: query has no destination for result data
SQL state: 42601
Hint: If you want to discard the results of a SELECT, use PERFORM instead.
Context: PL/pgSQL function "tst_dates_func" line 3 at SQL statement

这是我创建的函数：

CREATE OR REPLACE FUNCTION tst_dates_func() 
    RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$   
BEGIN
    select a.date_value, a.date_id, a.date_desc from dates_tbl a;
END;
$BODY$
      LANGUAGE plpgsql;

我不知道为什么我会收到上述错误。我想运行select * from tst_dates_func();并获取数据。或者根据需要进一步加入结果集。这里有什么问题？

Answer 1

做它作为纯SQL

CREATE OR REPLACE FUNCTION tst_dates_func() 
    RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$   
    select a.date_value, a.date_id, a.date_desc from dates_tbl a;

$BODY$
      LANGUAGE sql;

如果你真的需要plpgsql使用return query

CREATE OR REPLACE FUNCTION tst_dates_func() 
    RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$   
BEGIN
    perform SELECT dblink_connect('remote_db');
    return query
    select a.date_value, a.date_id, a.date_desc from dates_tbl a;

END;
$BODY$
      LANGUAGE plpgsql;