Zumero for SQL Server automatically syncs foreign key constraints. Shameless, blatantly self-serving commercial remark This is a handy feature that I really wish SQL Server had. Means that its enforcement is postponed until the transaction is committed. SQLite allows a foreign key constraint to be deferred, which SQLite does support ON DELETE and ON CASCADE. SQLite supports simple foreign keys (with one column referencing oneĬolumn), or composite foreign keys (with multiple columns referencing Full documentation is available on the SQLite website, but there are a few things worth highlighting. Similar to what a SQL Server dev would expect. Once you've got the feature turned on, foreign key support in SQLite is generally Here is a relevant quote from the SQLite Foreign Key Support1 page: 'If foreign key constraints are enabled when it is prepared, the DROP TABLE command performs an implicit DELETE to remove all rows from the table before dropping it. Which (1) opens the SQLite connection and (2) immediately executes the PRAGMA I get 'Error: foreign key constraint failed' when executing COMMIT. To enable the enforcement of foreign key constraints, execute the following SQL statement, shortlyĪfter you open your SQLite database connection: How to turn SQLite foreign key support on Unless you disable the foreign key checks, you will be prevented from doing these things in a table referenced by a foreign key constraint. Such cases can be when you want to drop or truncate a table, when you want to migrate old data, etc. (Note, however, that future releases of SQLite might change so that foreign key constraints enabled by default. Support for foreign keys because the feature is turned off by default, to preserveīackward compatibility. Foreign key checks will prevent you from making database updates in tables that have foreign key constraints. R-44261-39702:Foreign key constraints are disabled by default (for backwards compatibility), so must be enabled separately for each database connection. It is easy to get the impression that SQLite still lacks You're wrong! This code should fail but doesn't!ĬREATE TABLE (other REFERENCES (pk) ) įair enough. Since version 3.6.19, released in October 2009. The topic: SQLite on mobile devices.) I can't use SQLite! It doesn't support foreign keys!Īctually, it does. It's always deleting my extra data although the same foreign key exists after the statement.(This entry is part of a series. It does not work if I wrap INSERT OR REPLACE in a transaction either. values because the database I import from has no sync timestamp or whatsoever and I would have to compare everything to find out what row I have to UPDATE / what to INSERT.īut here lies the problem: INSERT OR REPLACE is actually a DELETE followed by an INSERT and the delete part triggers the foreign key ON DELETE which I thought I could prevent by making the constraint DEFERRED. Now my idea was to simply INSERT OR REPLACE INTO base_data. The second table would look similar but has remote_id set as foreign key remote_id | extra_data1 | extra_data2 |. +-+-+-+-īesides the local_id everything would just be a mirror of the remote database (I'll probably add a sync timestamp but that does not matter now). The first table (let's call it base_data) would look like local_id | remote_id | base_data1 | base_data2 |. I was thinking about splitting the data into two tables and join them afterwards so I can just dump the whole import into one table replacing everything that changed and manage the extra data separately since that does not change on import. Since there is no INSERT OR UPDATE I came up with this: It doesn't appear to have explicitly deferrable constraints, but I also don't know how uniqueness is enforced by default (for example, if it's already post-transaction this wouldn't matter anyway. Still trying to track down an answer for MongoDB. To summarize, we can prevent foreign keys from being properly enforced if we declare the constraints to be deferred and we leave lingering statement handles open. Looks like it's unsupported in MySQL and SQLite, unfortunately. I am currently trying to create an sqlite database where I can import a table from another sqlite database (can't attach) and add some extra data to each column. Also, if you declare the foreign key constraint to be immediate instead of deferred, the last call to sqlite3step will return SQLITECONSTRAINT.
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