ON CONFLICT

Updated: May 06, 2022

Deal with a conflict

Synopsis:

 ON CONFLICT { ROLLBACK | ABORT | FAIL | IGNORE | REPLACE } 

Description:

The ON CONFLICT clause is not a separate SQL command. It is a non-standard clause that can appear in many other SQL commands. It is given its own section in this document because it is not part of standard SQL and therefore might not be familiar.

The syntax for the ON CONFLICT clause is as shown for the CREATE TABLE command. For the INSERT and UPDATE commands, the keywords ON CONFLICT are replaced by OR, to make the syntax seem more natural. For example, instead of INSERT ON CONFLICT IGNORE we have INSERT OR IGNORE. The keywords change, but the meaning of the clause remains the same.

The ON CONFLICT clause specifies an algorithm for resolving constraint conflicts:
ROLLBACK
When a constraint violation occurs, an immediate ROLLBACK occurs, thus ending the current transaction, and the command aborts with a return code of SQLITE_CONSTRAINT. If no transaction is active (other than the implied transaction that is created on every command) then this algorithm works the same as ABORT.
ABORT
When a constraint violation occurs, the command backs out any prior changes it might have made and aborts with a return code of SQLITE_CONSTRAINT. No ROLLBACK is executed, so changes from prior commands within the same transaction are preserved. This is the default behavior.
FAIL
When a constraint violation occurs, the command aborts with a return code of SQLITE_CONSTRAINT. Any changes to the database that the command made prior to encountering the constraint violation are preserved and are not backed out. For example, if an UPDATE statement encountered a constraint violation on the 100th row that it attempts to update, then the first 99 row changes are preserved but changes to rows 100 and beyond never occur.
IGNORE
When a constraint violation occurs, the one row that contains the constraint violation is not inserted or changed, but the command continues executing normally. Other rows before and after the row that contained the constraint violation continue to be inserted or updated normally. No error is returned.
REPLACE
When a UNIQUE constraint violation occurs, the pre-existing rows that are causing the violation are removed prior to inserting or updating the current row. Thus, the insertion or update always occurs and the command continues executing normally. No error is returned. If a NOT NULL constraint violation occurs, the NULL value is replaced by the default value for that column. If the column has no default value, then the ABORT algorithm is used. If a CHECK constraint violation occurs, then the IGNORE algorithm is used.
Note: When this conflict resolution strategy deletes rows in order to satisfy a constraint, it doesn't invoke delete triggers on those rows. This may change in a future release.

The algorithm specified in the OR clause of an INSERT or UPDATE command overrides any algorithm specified in a CREATE TABLE. If no algorithm is specified anywhere, the ABORT algorithm is used.