更新时间:2023-01-29 09:57:46
首先,作为一次性数据清理练习,删除孤立的行,例如
First, as a one-time data-scrubbing exercise, delete the orphaned rows e.g.
DELETE
FROM ReferencingTable
WHERE NOT EXISTS (
SELECT *
FROM MainTable AS T1
WHERE T1.pk_col_1 = ReferencingTable.pk_col_1
);
其次,作为一次性模式更改练习,将 ON DELETE CASCADE
引用操作添加到引用表上的外键,例如
Second, as a one-time schema-alteration exercise, add the ON DELETE CASCADE
referential action to the foreign key on the referencing table e.g.
ALTER TABLE ReferencingTable DROP
CONSTRAINT fk__ReferencingTable__MainTable;
ALTER TABLE ReferencingTable ADD
CONSTRAINT fk__ReferencingTable__MainTable
FOREIGN KEY (pk_col_1)
REFERENCES MainTable (pk_col_1)
ON DELETE CASCADE;
然后,当引用表中的行被删除时,引用表中的行将永远被删除.
Then, forevermore, rows in the referencing tables will automatically be deleted when their referenced row is deleted.