不建议使用rowid作为sqlite主键

前端之家收集整理的这篇文章主要介绍了不建议使用rowid作为sqlite主键前端之家小编觉得挺不错的,现在分享给大家,也给大家做个参考。

If you don’t want to read the whole post then just do this: Everytime you create a table with sqlite make sure to haveanINTEGER PRIMARY KEY AUTOINCREMENTcolumn (the rowid columnwill be an alias to this one).

If you have some time then read on…

A lot of people don’t realize thata rowidcan change. As always a simple example worths more than1000 words. You can test this example withSQLiteManager.

Create a table without a primary key:
CREATE TABLE test (name TEXT);

Insert some data into the table:
INSERT INTO test (name) VALUES (‘marco’);
INSERT INTO test (name) VALUES (‘giuly’);
INSERT INTO test (name) VALUES (‘gregory’);
INSERT INTO test (name) VALUES (‘house’);

Perform a SELECT rowid,* FROM test;
Here you go the result:
1marco
2giuly
3gregory
4house

Everything seems OK (until now…)
Now delete a couple of rows:
DELETE FROM test WHERE name=’marco’;
DELETE FROM test WHERE name=’gregory’;

Now perform again: SELECT rowid,* FROM test;
Here it is the result:
2giuly
4house

Everything is fine,no?
That’s cool…

Now,perform a VACUUM on the database and run again thequery:
SELECT rowid,* FROM test;
Here it is the result:
1giuly
2house

Rowids are changed!!!! So please take extra care when you define atable and need to reference records using rowids. From the official documentation: “Rowids can change at any time andwithout notice. If you need to depend on your rowid,make it anINTEGER PRIMARY KEY,then it is guaranteed not to change”. And Iadd also AUTOINCREMENT so you are sure that the same rowid(s) arenot reused when rows are deleted.

原文链接:https://www.f2er.com/sqlite/200294.html

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