PostgreSQL存储过程数据参数

Question

我有以下存储过程,它返回0结果,但如果单独运行查询,则会产生大量结果.我错过了什么.

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结果

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

返回100+结果

Answer 1

您将baselineDate参数声明为date:

CREATE OR REPLACE FUNCTION countStatistics(baselineDate Date)

但用它作为timestamp:

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

你得到一个隐式转换,所以countStatistics('2015-01-01 01:00:00')实际上会执行这个SQL:

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

并且,在date隐含地回归到a之后timestamp,它实际上将是这样的:

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)