mysql - MySQL は複数のテーブルから行を削除します

Question

これは正しい方法ですか？

DELETE t1, t2, t3, t4 FROM 
  table1 as t1 
  INNER JOIN  table2 as t2 on t1.id = t2.id
  INNER JOIN  table3 as t3 on t1.id=t3.id
  INNER JOIN  table4 as t4 on t1.id=t4.id
  WHERE  t1.username='%s' AND t1.id='%s'

Answer 1

はい、そうです。ここでうまく動作します：

CREATE TABLE table1 (id int, username nvarchar(30));
CREATE TABLE table2 (id int);
CREATE TABLE table3 (id int);
CREATE TABLE table4 (id int);

INSERT INTO table1 VALUES (1, 'Foo'),(2, 'Bar');
INSERT INTO table2 VALUES (1),(2);
INSERT INTO table3 VALUES (1),(2);
INSERT INTO table4 VALUES (1),(2);

SELECT COUNT(*) FROM table1;
2
SELECT COUNT(*) FROM table2;
2
SELECT COUNT(*) FROM table3;
2
SELECT COUNT(*) FROM table4;
2

DELETE t1, t2, t3, t4 FROM
  table1 as t1
  INNER JOIN  table2 as t2 on t1.id = t2.id
  INNER JOIN  table3 as t3 on t1.id=t3.id
  INNER JOIN  table4 as t4 on t1.id=t4.id
  WHERE  t1.username='Foo' AND t1.id='1';

SELECT COUNT(*) FROM table1;
1
SELECT COUNT(*) FROM table2;
1
SELECT COUNT(*) FROM table3;
1
SELECT COUNT(*) FROM table4;
1

うまくいかない場合は、この例を変更して、どのような問題が発生しているかを示すことができます。

Answer 2

それを理解する簡単な方法は、最初にそれをクエリとして書くことです:

SELECT * FROM 
        table1 as t1 
        INNER JOIN  table2 as t2 on t1.id = t2.id
        INNER JOIN  table3 as t3 on t1.id=t3.id
        INNER JOIN  table4 as t4 on t1.id=t4.id
        WHERE  t1.username='%s' AND t1.id='%s'

期待どおりの結果が得られたら、*Select ** を Delete とテーブル名に置き換えてください。次に、次のようになります。

Delete t1, t2, t3, t4 From table1 as t1 
        INNER JOIN  table2 as t2 on t1.id = t2.id
        INNER JOIN  table3 as t3 on t1.id=t3.id
        INNER JOIN  table4 as t4 on t1.id=t4.id
        WHERE  t1.username='%s' AND t1.id='%s'