If a NOT NULL constraint violation occurs, it replaces the NULL value with the default value for that column, or if the column has no default value, then the ABORT algorithm is used.When a UNIQUE or PRIMARY KEY constraint violation occurs, the REPLACE option deletes pre-existing rows that are causing the constraint violation prior to inserting or updating the current row and the command continues executing normally.The REPLACE option works differently depending on the violation: The first examples on this page use IGNORE, but here it is again. However, this option works like ABORT for foreign key constraint errors. No error is returned for uniqueness, NOT NULL, and UNIQUE constraint errors when this option is used. Other rows before and after the row that contained the constraint violation are inserted or updated normally. The IGNORE option skips the one row that contains the constraint violation and continues processing subsequent rows of the SQL statement as if nothing went wrong. INSERT OR FAIL INTO Products VALUES (6, 'Bandage', 120.00) INSERT OR FAIL INTO Products VALUES (5, 'Chisel', 23.00) INSERT OR FAIL INTO Products VALUES (4, 'Wrench', 37.00) INSERT OR FAIL INTO Products VALUES (3, 'Saw', 11.34) INSERT OR FAIL INTO Products VALUES (2, NULL, 1.49) INSERT OR FAIL INTO Products VALUES (1, 'Hammer', 9.99) Here it is in with separate INSERT statements within a transaction. But it does not back out prior changes of the SQL statement that failed nor does it end the transaction. The FAIL option aborts the current SQL statement with an SQLITE_CONSTRAINT error. INSERT OR ABORT INTO Products VALUES (6, 'Bandage', 120.00) INSERT OR ABORT INTO Products VALUES (5, 'Chisel', 23.00) INSERT OR ABORT INTO Products VALUES (4, 'Wrench', 37.00) INSERT OR ABORT INTO Products VALUES (3, 'Saw', 11.34) INSERT OR ABORT INTO Products VALUES (2, NULL, 1.49) INSERT OR ABORT INTO Products VALUES (1, 'Hammer', 9.99) Here’s what happens if I put each row in its own INSERT statement within a transaction. No results were returned because the INSERT operation was aborted, and the table is therefore empty. Here’s an example of what happens when you specify ABORT. In other words, this is what happens during constraint violations when you don’t use the ON CONFLICT clause. This option aborts the current SQL statement with an SQLITE_CONSTRAINT error and backs out any changes made by the current SQL statement but changes caused by prior SQL statements within the same transaction are preserved and the transaction remains active. This is just one of five possible options for this clause.īelow are examples using each of the five options. In these examples I used the IGNORE option. So we get the same result as in the previous example. Now I’ll insert the same data and use OR IGNORE to skip over the row that violates the constraint. To demonstrate, I’ll drop the previous table and create it again, but without the ON CONFLICT clause: DROP TABLE IF EXISTS Products The difference is that, you replace ON CONFLICT with OR. You can also use this clause when inserting and updating data. Now if I try to insert NULL into the ProductName column that row is skipped. In this case I specified IGNORE, which means that, if there’s a constraint violation SQLite will skip over that row and then continue processing. In this case, I added the clause to a NOT NULL constraint. When you use the ON CONFLICT clause, you apply it to the specific constraint that you want to handle. Here’s an example of using ON CONFLICT at the time of creating the table. When Creating the TableĪs mentioned, you can use ON CONFLICT when you create the table or when you insert/update data. The ON CONFLICT clause is used in CREATE TABLE statements, but it can also be used when inserting or updating data by replacing ON CONFLICT with OR. This article provides examples and an explanation of each of these options. There are five possible options you can use with this clause: It applies to UNIQUE, NOT NULL, CHECK, and PRIMARY KEY constraints (but not FOREIGN KEY constraints). SQLite has the ON CONFLICT clause that allows you to specify how to handle constraint conflicts.
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