Question

我正在使用SQLiteDatabase作为Java库，我需要支持一个非常低版本的Android API（v4），它不附带支持外键的SQLite版本。

因此，为了删除顶级数据及其所有儿童＆＃34;，我需要删除这些孩子，然后以这种方式手动重现与外国人相同的效果关键约束ON DELETE CASCADE

我尝试做的是使用delete api的以下SQL。

DELETE FROM childTable 
WHERE someFK IN (
    SELECT parent_id 
    FROM parentTable 
    WHERE someFlag = 1
)

我提出的初始解决方案是在我的where子句中对select查询进行硬编码，如下所示，但是由于SQLiteDatabase api支持查询，execSQL等，这个解决方案我用得非常错误且使用起来很危险？解决方法：

String[] whereArgs = {Integer.toString(1)};
this.database.delete(TABLE_CHILD_ONE, COL_ONE_FK_SESSION+" IN (SELECT "+COL_SESSION_ID+" FROM "+TABLE_SESSIONS+" WHERE "+COL_SESSION_DONE+"=?)", whereArgs);
this.database.delete(TABLE_CHILD_TWO, COL_TWO_FK_SESSION+" IN (SELECT "+COL_SESSION_ID+" FROM "+TABLE_SESSIONS+" WHERE "+COL_SESSION_DONE+"=?)", whereArgs);
this.database.delete(TABLE_CHILD_THREE, COL_THREE_FK_SESSION+" IN (SELECT "+COL_SESSION_ID+" FROM "+TABLE_SESSIONS+" WHERE "+COL_SESSION_DONE+"=?)", whereArgs);

Answer 1

您可以为每个表创建触发器：

CREATE TRIGGER delete_cascade AFTER DELETE ON parentTable
BEGIN
    DELETE FROM childTable child WHERE child.parent_id=OLD.id;
END;

在交易中运行。

More about triggers

SQLiteDatabase删除涉及子查询

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