如何設置一個數組作爲一個mysql用戶變量

Question

我沒有想到會發現這很難，但我試圖在MySQL中設置一個用戶變量來包含一個值的數組。我不知道如何做到這一點，所以試着做一些研究，很驚訝地發現沒有答案。我曾嘗試：

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

的原因是我想用變量在下面的語句後面：

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; 

將是幫助，非常感謝。

---

快進了一會兒，我結束了以下的快速和骯髒的解決方案，它並沒有給我的靈活性，再使用陣列其他地方的代碼，但嘿，這是一個不可充電管理任務，所以我不要我不想花更多的時間在它上面。

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似乎已經找到了最完美的解決方案（沒有測試它自己還沒有），但我正在寫一些東西，呼籲這個下次我會記得測試一下吧！

Answer 1

就找到了答案在這裏：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

正如馬克B中提及的，存在MYSQL沒有數組變量。

到FIND_IN_SET解決方案的替代方案是使用選擇與UNION模擬陣列：

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，你的查詢將看起來像這樣：

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

如果用戶具有CREATE TABLE特權，則可以通過創建臨時單列表來模擬數組。可以使用SELECT語句檢索表中的一個或多個值。臨時表會在會話結束時被刪除，但一旦不再需要時，明確地刪除它們是個好主意。

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;