将行添加到外键后我无法删除行 [英] I can't delete row after append it a foreign key

问题描述

我有两个表second和third

second_id(PRIMARY KEY)  second_name           
   1                    .........
   2                    .......
   3                    .........

third_id(PRIMARY KEY) third_name second_id(FOREIGN KEY for second.second_id)
      1                  .....                 1
      2                  .....                 1
      3                  .....                 1
      4                  .....                 2
      5                  .....                 2

现在我想从second其中second_id=2( DELETE FROM second WHERE second_id=2 )删除一行，但是它不起作用.它说 Successful 0 row(s) affected ，而且是在我向third.second_id附加外键之后发生的(在创建表后添加了外键).

Now i want to delete a row fromsecond where second_id=2 (DELETE FROM second WHERE second_id=2) but it does not work. It says Successful 0 row(s) affected What is more is, it happened after i append a foreign key to third.second_id (i added foreign key after table is created).

推荐答案

您将必须删除third表中具有second_id = 2的行，然后从second中删除id = 2或具有在外键约束中

You will have to delete the rows in third table with second_id = 2 and then delete the rows from second with id = 2 or have ON DELETE CASCADE in the foreign key constraint

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