Question

我正在尝试在PostgreSQL 9.3.5中实现一个日期作为参数的函数它应涵盖以下所有条件并相应地返回结果。

select * from tablename
where sid is not null and dob >= '11-14-2014' order by dob;
-- Only Start Date

select * from tablename
where sid is not null and dob <= '11-21-2014' order by dob;
-- Only End Date

select * from tablename
where sid is not null and dob between '11-10-2014' and '11-21-2014' order by dob; 
-- Both Start and End Dates are Given

select * from tablename
where sid is not null and dob is null; 
-- Both Start and End Dates are Null

SQL Fiddle

但我上面的SQL Fiddle没有按预期工作。

我希望有一个通用实现，这样如果明天我在标准搜索中有更多new Date Fields，那么我可以将它们添加到where condition中，但不能添加到IF的每一行中1}}陈述。

Updated SQL Fiddle

Answer 1

这可以 更简单 ：

您可以简化@ Clodoaldo目前接受的答案：

SELECT *
FROM   sampletest
WHERE  eid IS NOT NULL
AND   (_sd IS NULL AND _ed IS NULL OR
       _sd IS NULL AND dob <= _ed  OR
       _ed IS NULL AND dob >= _sd  OR
       dob BETWEEN _sd AND _ed);

比较dob >= _sd后，无需另外检查_sd is not null 无论如何，表达式只能评估为TRUE非空_sd。

但这些都不是必要的：

CREATE OR REPLACE FUNCTION test_dob_dates(_sd date, _ed date)
  RETURNS SETOF sampletest AS
$func$
SELECT *
FROM   sampletest
WHERE  eid IS NOT NULL
AND    dob BETWEEN COALESCE(_sd, -infinity) AND COALESCE(_ed, infinity)
$func$ LANGUAGE sql STABLE;

不要引用语言名称。这是一个标识符。
Postgres为timestamp和date类型提供special values -infinity and infinity。您只需使用COALESCE默认使用这些值。

SQL Fiddle（第9.3页）。

除此之外：我建议使用标准ISO日期 '2014-11-10' ，而不是 ~~'11-10-2014'~~ ，这可能是不明确的，并打破了不同的区域设置设置。 The manual advises as much.

Answer 2

您必须将函数定义为返回set of sampletest，然后根据传递的参数返回return different query restults。

CREATE FUNCTION
  test_dob_dates(_sd date, _ed date)
RETURNS
  SETOF sampletest
AS
  $BODY$
    BEGIN
      IF _sd IS NOT NULL AND _ed IS NOT NULL THEN
        RETURN QUERY SELECT * FROM sampletest WHERE dob BETWEEN _sd AND _ed;
      ELSIF _sd IS NULL AND _ed IS NULL THEN
        RETURN QUERY SELECT * FROM sampletest WHERE dob IS NULL;
      ELSEIF _ed IS NOT NULL THEN
        RETURN QUERY SELECT * FROM sampletest WHERE dob <= _ed;
      ELSE
        RETURN QUERY SELECT * FROM sampletest WHERE dob >= _sd;
      END IF;
    END;
  $BODY$
LANGUAGE
  'plpgsql' VOLATILE;

eid IS NOT NULL子句似乎是多余的，因为您已将eid定义为PRIMARY KEY，这意味着它永远不会为NULL。

Answer 3

SQL Fiddle

create function test_dob_dates(_sd date, _ed date)
returns setof sampletest as $body$
    select *
    from sampletest
    where
        eid is not null
        and (
            (_sd is null and _ed is null)
            or (_sd is not null and _ed is null and dob >= _sd)
            or (_sd is null and _ed is not null and dob <= _ed)
            or dob between _sd and _ed
        );
$body$ language sql stable;

日期为params的函数可以为NULL

3 个答案: