SQLite查询从多个表中删除

Question

我使用查询来检索具有特定列名称的表列表:

select name from sqlite_master where type='table' and sql like '%unique_col_id%';

因此,它返回一个表名列表,例如table_1,table_2,table_3 ..

我想删除上表中所有行,其中unique_col_id等于特定值:

DELETE FROM table_1 where unique_col_id=3;
DELETE FROM table_2 where unique_col_id=3;
DELETE FROM table_3 where unique_col_id=3;

有没有办法在一个查询中删除所有表？我的意思是集成两个查询(搜索表并删除所有这些查询与unique_col_id = 3 ......)

谢谢

Answer 1

虽然我确信有一些方法可以在一个语句中完成所有这些,但最好使用事务和/或触发器.

事务允许您将一堆语句组合在一起,以便在它们全部运行之前不会保存任何内容.在交易完成之前,没有其他流程会看到您的更改.如果出现错误或您的流程在交易过程中死亡,则会抛弃所有更改.这避免了一大堆问题.使用事务可以让你使用简单的语句,而不是试图将所有内容粉碎成一个无法维护的混乱.

begin;
DELETE FROM table_1 where unique_col_id=3;
DELETE FROM table_2 where unique_col_id=3;
DELETE FROM table_3 where unique_col_id=3;
commit;

用触发器来补充它.这使得数据库可以在发生某些事情时自动执行操作,例如当您从一个表中删除列时,它可以从其他表中删除相关信息.最常见的方法是设置ON DELETE CASCADE外键.

# This is necessary in SQLite else foreign keys will be ignored
sqlite> pragma foreign_keys = on;

# Make two tables with a relationship and set it ON DELETE CASCADE
sqlite> create table addresses ( id INTEGER PRIMARY KEY, address TEXT, person REFERENCES people(id) ON DELETE CASCADE );
sqlite> create table people ( id INTEGER PRIMARY KEY, name TEXT );

# Add a row with a relationship.
sqlite> insert into people (name) VALUES ("Foo Bar");
sqlite> select * from people;
1|Foo Bar
sqlite> insert into addresses (address, person) VALUES ("123 Foo St", 1);
sqlite> select * from people join addresses on addresses.person = people.id;
1|Foo Bar|1|123 Foo St|1

# Delete the parent row and the child (address) is also deleted.
sqlite> delete from people where id = 1;
sqlite> select * from people;
sqlite> select * from addresses;

这更加强大.对数据库进行更改的人不需要知道所有细节,数据库会为他们处理.