A conflict can occur when trying to insert a row with a
primary key or unique index that already exists in the table, or when trying to update a row that does not exist. In such cases, the
ON CONFLICT clause can be used to specify how to handle the conflict.
The syntax for the ON CONFLICT clause is as follows:
INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...) ON CONFLICT conflict_action;
Here, table_name is the name of the table, column1, column2, and so on are the names of the columns being inserted, and value1, value2, and so on are the corresponding values being inserted.
The conflict_action can be one of the following:
ROLLBACK: This option rolls back the entire transaction if a conflict occurs. This is the default behavior if the ON CONFLICT clause is not specified.
ABORT: This option aborts the current statement and rolls back any changes that were made before the conflict occurred.
FAIL: This option aborts the current statement, but does not roll back any changes that were made before the conflict occurred.
IGNORE: This option ignores the conflict and continues with the insertion. If a unique constraint is violated, then the row with the conflict is not inserted, but the rest of the rows are inserted.
REPLACE: This option replaces the existing row with the new row being inserted. If the row does not exist, then it is inserted as usual.
ON CONFLICT clause can also be used with the
UPDATE statement to specify what action should be taken if no rows are affected by the update. The syntax for the
ON CONFLICT clause with the update statement is as follows:
UPDATE table_name SET column1 = value1, column2 = value2, ... WHERE condition ON CONFLICT conflict_action;
Here, table_name is the name of the table, column1, column2, and so on are the names of the columns being updated, and value1, value2, and so on are the corresponding values being updated. The condition specifies which rows to update.
In conclusion, the
ON CONFLICT clause in SQLite is a powerful tool for handling conflicts that may arise when inserting or updating data in a table. By specifying an appropriate conflict action, you can ensure that your database remains consistent and reliable.