相关疑难解决方法(0)

我有一个sql函数,它执行一个简单的sql select语句:

CREATE OR REPLACE FUNCTION getStuff(param character varying)
  RETURNS SETOF stuff AS
$BODY$
    select *
    from stuff
    where col = $1
$BODY$
  LANGUAGE sql;

现在我调用这个函数是这样的:

select * from getStuff('hello');

如果我需要订购并限制结果order by和limit条款,我有哪些选择？

我想这样的查询:

select * from getStuff('hello') order by col2 limit 100;

效率不高,因为表中的所有行都stuff将由函数返回,getStuff然后按限制排序和切片.

但即使我是对的,如何通过sql语言函数的参数传递顺序也没有简单的方法.只能传递值,而不能传递sql语句的一部分.

另一种选择是用plpgsql语言创建函数,在那里可以构造查询并通过它来执行EXECUTE.但这也不是一个非常好的方法.

那么,有没有其他方法可以实现这一目标？或者你会选择什么选择？在函数外部订购/限制,还是plpgsql？

我正在使用postgresql 9.1.

编辑

我修改了CREATE FUNCTION语句,如下所示:

CREATE OR REPLACE FUNCTION getStuff(param character varying, orderby character varying)
  RETURNS SETOF stuff AS
$BODY$
    select t.* …

运行PostgreSQL(7.4和8.x),我认为这是有效的,但现在我遇到了错误.

我可以单独运行查询,它工作正常,但如果我UNION或UNION ALL它会抛出一个错误.

这个错误输出:(警告:pg_query():查询失败:错误:列"Field1"不存在... ORDER BY CASE"Field1"W ...)

SELECT "Field1" AS field_1, "Field2" AS field_2,
"Field3" AS field_3, "Field4" AS field_4
FROM "TableName" 
WHERE condition
AND other_condition
UNION ALL
SELECT "Field1" AS field_1, "Field2" AS field_2,
"Field3" AS field_3, "Field4" AS field_4
FROM "TableName" 
WHERE yet_another_condition
AND yet_another_other_condition
ORDER BY CASE "Field1"
    WHEN 'A' THEN 1
    WHEN 'B' THEN 2
    WHEN 'C' THEN 3
    ELSE 4
END

这有效:

SELECT "Field1" AS field_1, "Field2" AS field_2,
"Field3" AS field_3, "Field4" AS …