PostgreSQL 存储过程数据参数

Question

我有以下存储过程，它返回 0 个结果，但如果单独运行查询，则会产生大量结果。我缺少什么。

CREATE OR REPLACE FUNCTION countStatistics(baselineDate Date) RETURNS int AS $$
DECLARE
    qty int;
BEGIN
    SELECT COUNT(*) INTO qty FROM statistics WHERE time_stamp = baselineDate;
    RETURN qty;
END;
$$ LANGUAGE plpgsql;

--Execute the function
SELECT countStatistics('2015-01-01 01:00:00') as qty;

返回 0 个结果

SELECT COUNT(*) FROM statistics WHERE time_stamp = '2015-01-01 01:00:00';

返回 100+ 个结果

Answer 1

您将 baselineDate 参数声明为 date：

CREATE OR REPLACE FUNCTION countStatistics(baselineDate Date)

但将其用作 timestamp：

SELECT COUNT(*) INTO qty FROM statistics WHERE time_stamp = baselineDate;

您将获得隐式转换，因此 countStatistics('2015-01-01 01:00:00') 将实际执行此 SQL：

SELECT COUNT(*) INTO qty FROM statistics WHERE time_stamp = '2015-01-01';

并且在 date 隐式转换回timestamp，它实际上是这样的：

SELECT COUNT(*) INTO qty FROM statistics WHERE time_stamp = '2015-01-01 00:00:00';

尝试更改函数声明以使用timestamp：

CREATE OR REPLACE FUNCTION countStatistics(baselineDate timestamp)