sqlite中的递归外键

Question

在sqlite中是否允许自引用或递归外键？有没有特殊的语法来实现这一目标？到目前为止,我尝试了以下无济于事:FOREIGN KEY(ParentPrimaryKeyId) REFERENCES ThisTableName(PrimaryKeyId)

作为参考,我的目标是iOS 4中的sqlite 3.6.22.

Answer 1

是的sqlite支持自引用外键,例如:

sqlite> PRAGMA foreign_keys = ON;
sqlite> CREATE TABLE SomeTable (
   ...>     id INTEGER PRIMARY KEY AUTOINCREMENT,
   ...>     parent_id INTEGER, 
   ...>     FOREIGN KEY(parent_id) REFERENCES SomeTable(id));
sqlite> INSERT INTO SomeTable (parent_id) VALUES (234324);
Error: foreign key constraint failed
sqlite> INSERT INTO SomeTable (parent_id) VALUES (NULL);
sqlite> SELECT * FROM SomeTable;
1|
sqlite> INSERT INTO SomeTable (parent_id) VALUES (1);
sqlite> SELECT * FROM SomeTable;
1|
2|1
sqlite>