![]() ![]() It simply tries to add a record, and if that fails because of a constraint then it will try to update whatever record is causing the constraint to kick in. If you do not, a query for a non-existent tag will do a full table scan. Okay, so SQLite doesn't use any column to select specific rows that it will try to update. The exceptional behaviors defined in this paragraph might change in a future release. SELECT EXISTS (SELECT 1 FROM myTbl WHERE utag'tag' LIMIT 1) Selecting 1 is the accepted practice if you don't need something from the record, though what you select shouldn't really matter either way. Nor does REPLACE increment the change counter. The update hook is not invoked for rows that are deleted by the REPLACE conflict resolution strategy. When the REPLACE conflict resolution strategy deletes rows in order to satisfy a constraint, delete triggers fire if and only if recursive triggers are enabled. Define your SQL schema to only allow unique data for this column. Manually check if the data already exists then added it if it doesn't exist. If a CHECK constraint violation occurs, the REPLACE conflict resolution algorithm always works like ABORT. There are two basic ways you can do this: Query the database. If a NOT NULL constraint violation occurs, the REPLACE conflict resolution replaces the NULL value with he default value for that column, or if the column has no default value, then the ABORT algorithm is used. When a UNIQUE constraint violation occurs, the REPLACE algorithm deletes pre-existing rows that are causing the constraint violation prior to inserting or updating the current row and the command continues executing normally. Use INSERT OR REPLACE which does exactly what you want : insert a new row when the name does not exists or update otherwise. ![]() ') if db.rowcount 0: db.execute ('INSERT. Essentially, it is based on UNIQUE and NOT NULL constraints (primary keys being rather usual as a constraint to select whether to update or insert). If your language allows to read the number of affected rows, it is possible to do this with two SQL commands: db.execute ('UPDATE. See the CONFLICT clause documentation for how this is dealt with.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |