從多個表中刪除使用順序和限制

Question

我想從兩個表中刪除使用ORDER BY DESC和LIMIT有關係的表。

DELETE FROM my_rel_table AS t1 
LEFT JOIN my_photo_table AS t2 ON t2.typeid = t1.typeid 
WHERE t1.relid = 1 
AND t1.type = 1 
ORDER BY t1.id DESC 
LIMIT 1 

很明顯，以上不起作用，因爲mysql不接受命令，並限制使用內部連接。

表結構如下：

my_rel_table 
id relid relno typeid type 
int int int int tinyint 

my_photo_table 
typeid pos_x pos_y width height 
int int int int int 

Answer 1

使用JOIN對一個子查詢，以獲得從my_rel_table

DELETE my_rel_table, my_photo_table 
FROM my_rel_table 
INNER JOIN 
(
    SELECT MAX(id) AS MaxId 
    FROM my_rel_table 
    WHERE relid = 1 
    AND type = 1 
) Sub1 
ON my_rel_table.id = Sub1.MaxId 
LEFT OUTER JOIN my_photo_table ON my_photo_table.typeid = my_rel_table.typeid 
WHERE my_rel_table.relid = 1 
AND my_rel_table.type = 1 

不直接測試，因爲我沒有測試數據的最高ID這樣做！

編輯 - 嘗試做前5名的夫婦，但同樣沒有測試

DELETE my_rel_table, my_photo_table 
FROM my_rel_table 
INNER JOIN 
(
    SELECT id 
    FROM my_rel_table 
    WHERE relid = 1 
    AND type = 1 
    ORDER BY id DESC 
    LIMIT 5 
) Sub1 
ON my_rel_table.id = Sub1.id 
LEFT OUTER JOIN my_photo_table ON my_photo_table.typeid = my_rel_table.typeid 
WHERE my_rel_table.relid = 1 
AND my_rel_table.type = 1 

或者以不同的方式。

DELETE my_rel_table, my_photo_table 
FROM my_rel_table 
INNER JOIN 
(
    SELECT id, @Counter:=@Counter+1 AS ItemCounter 
    FROM my_rel_table 
    CROSS JOIN (SELECT @Counter:=0) Sub1 
    WHERE relid = 1 
    AND type = 1 
    ORDER BY id DESC 
) Sub1 
ON my_rel_table.id = Sub1.id 
AND Sub1.ItemCounter <= 5 
LEFT OUTER JOIN my_photo_table ON my_photo_table.typeid = my_rel_table.typeid 
WHERE my_rel_table.relid = 1 
AND my_rel_table.type = 1