sqlserver查询多个分类的最新时间数据

sqlserver查询数据表中每个类别最新的一条记录 | SQL

表tariff_info, 原始数据:

想要的结果:以start_time时间倒序排序, 以code分类, 查询每一类最新的一条记录

sql:

SELECT

    a.*

FROM

    TARIFF_INFO a,

    (

        SELECT

            code,

            MAX (start_time) start_time

        FROM

            TARIFF_INFO

        GROUP BY

            code

    ) b

WHERE

    a.start_time = b.start_time

AND a.code = b.code

ORDER BY

    a.code

这样查询结果已经实现了, 但是需要添加过滤条件, 即当前时间在start_time和end_time之间.  如果还用上面的sql仅仅在末尾追加一个条件发现查询结果为空:

所以必须在子查询中添加同样的过滤条件方可查出正确结果, 如下面sql:

SELECT

    a.*

FROM

    TARIFF_INFO a,

    (

        SELECT

            code,

            MAX (start_time) start_time

        FROM

            TARIFF_INFO

        WHERE

            start_time <= '2018-09-18'

        GROUP BY

            code

    ) b

WHERE

    a.start_time = b.start_time

AND a.code = b.code

AND a.start_time <= '2018-09-18'

ORDER BY

    a.code

另:需要注意sql中时间区间的比较<=貌似有临界日期会漏掉的情况, 这里不作赘述了.以下sql和上面的异曲同工:

SELECT

    a.*

FROM

    TARIFF_INFO a

INNER JOIN (

    SELECT

        code,

        MAX (start_time) 'start_time'

    FROM

        TARIFF_INFO

    WHERE CONVERT(VARCHAR(10),start_time,121) <= '2018-09-18'

    GROUP BY

        code

) b ON a.code = b.code

AND a.start_time = b.start_time

AND CONVERT(VARCHAR(10),b.start_time,121) <= '2018-09-18'

ORDER BY

    a.code