Question

我没想到会发现这么困难，但我试图在MySQL中设置一个用户变量来包含一个值数组。我不知道如何做到这一点所以尝试做一些研究，并且很惊讶找不到答案。我试过了：

SET @billable_types = ['client1','client2','client3'];

原因是我想稍后在以下语句中使用该变量：

SELECT sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
    from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
    where date(tlg.time_start) >= @time_start
          and date(tlg.time_stop) <= @time_stop
          and mttl.type IN (@billable_types)
            and tlg.task_id = mttl.id
    group by start_date
    order by start_date desc;

非常感谢您的帮助。

快进一段时间，我最终得到了以下快速而肮脏的解决方案，这并没有给我在代码中其他地方重新使用数组的灵活性，但是嘿，这是一个不可完成的管理任务，所以我不想花更多的时间在上面。

SELECT WEEKDAY(tlg.time_start) AS day_of_week, date(tlg.time_start) as start_date,
                            sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
                    from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
                    where date(tlg.time_start) >= @time_start
                          and date(tlg.time_stop) <= @time_stop
                          and mttl.type IN ('c1','c2','c3')
                            and tlg.task_id = mttl.id
                    group by start_date
                    order by start_date desc;

joostschouten似乎已经找到了最优雅的解决方案（我自己还没有测试过）但是下次我正在写一些要求它的东西我会记得测试它！

Answer 1

刚刚在这里找到答案：How to cycle with an array in MySQL?

set @billable_types = 'client1,client2,client3';
select * from mttl where find_in_set(mttl.type, @billable_types);

Answer 2

正如Marc B所提到的，MYSQL中没有数组变量。

find_in_set 解决方案的替代方法是使用 SELECT 和 UNION 来模拟数组：

SELECT billable_type FROM (
  SELECT 'client1' AS billable_type UNION
  SELECT 'client2' AS billable_type UNION
  SELECT 'client3' AS billable_type) AS t

所以你的查询看起来像这样：

SELECT sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
     from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
     where date(tlg.time_start) >= @time_start
          and date(tlg.time_stop) <= @time_stop
          and mttl.type IN (

            SELECT billable_type FROM (
              SELECT 'client1' AS billable_type UNION
              SELECT 'client2' AS billable_type UNION
              SELECT 'client3' AS billable_type) AS t

          )
             and tlg.task_id = mttl.id
     group by start_date
     order by start_date desc;

Answer 3

如果用户具有CREATE TABLE权限，则可以通过创建临时单列表来模拟数组。可以使用SELECT语句检索表中的一个或多个值。临时表在会话结束时被删除，但是在不再需要它们时明确删除它们是个好主意。

CREATE TEMPORARY TABLE billable_types (c VARCHAR(16));
INSERT INTO billable_types VALUES ('client1'), ('client2'), ('client3');

SELECT sum((time_to_sec(timediff(tlg.time_stop, tlg.time_start))/3600)) as billable_hours
from mod_tmlog_time_log tlg, mod_tmlog_task_list mttl
where date(tlg.time_start) >= @time_start
      and date(tlg.time_stop) <= @time_stop
      and mttl.type IN (SELECT * FROM billable_types)
        and tlg.task_id = mttl.id
group by start_date
order by start_date desc;

DROP TABLE billable_types;

如何将数组设置为mysql用户变量

3 个答案: