![]() ![]() Now, let's demonstrate how the cascade delete works. ![]() In this example, we've created a foreign key (with cascade delete) called fk_departments that references the departments table based on the department_id field. INSERT INTO employees SELECT * FROM _employees_old Now, let's add a foreign key with cascade delete to the employees table: PRAGMA foreign_keys=off ĪLTER TABLE employees RENAME TO _employees_old INSERT INTO employees VALUES (10001, 'Anderson', 'Dave', 999) INSERT INTO employees VALUES (10000, 'Smith', 'John', 30) INSERT INTO departments VALUES (999, 'Sales') INSERT INTO departments VALUES (30, 'HR') Next, let's add some data to these tables: INSERT INTO table1 SELECT * FROM _table1_old įirst, let's start by creating our 2 tables ( departments and employees): The syntax to add a foreign key with cascade delete to an existing table in SQLite is: PRAGMA foreign_keys=off ĪLTER TABLE table1 RENAME TO _table1_old Instead you will need to rename the table, create a new table with the foreign key, and then copy the data into the new table. You can not use the ALTER TABLE statement to add a foreign key with cascade delete in SQLite. The first thing to say here is that SQLite has no syntax to change the settings of a column. How to Add a Foreign Key with Cascade Delete to an Existing Table Then we've created a foreign key called fk_departments on the employees table that references the departments table based on the department_id field.īecause of the cascade delete, when a record in the departments table is deleted, all records in the employees table will also be deleted that have the same department_id value. In this example, we've created a primary key on the departments table that consists of only one field - the department_id field. ( employee_id INTEGER PRIMARY KEY AUTOINCREMENT, ( department_id INTEGER PRIMARY KEY AUTOINCREMENT, Let's look at an example of how to create a foreign key with cascade delete using the CREATE TABLE statement in SQLite. REFERENCES parent_table (column1, column2. The syntax for creating a foreign key with cascade delete using a CREATE TABLE statement in SQLite is: CREATE TABLE table_nameįOREIGN KEY (column1, column2. I don't know if this helps, as I don't know what you are attempting to do with nr, but maybe it will.How to Create a Foreign Key with Cascade Delete using a CREATE TABLE statement Syntax ![]() Also, when you insert a new row, you can get the rowid assigned by SQLite using "SELECT last_insert_rowid()". You can access the rowid of any row directly as "rowid", "_rowid_" or "oid". The sole purpose of autoincrement in SQLite is to not reuse previously used record numbers (whether they have been deleted or not). In the first case, SQLite tracks maxrowid over the life of the database, and any new record is assigned maxrowid + 1 where maxrowid is the maximum rowid ever seen. ![]() So, for the second condition, for a new row, rowid = max(rowid) + 1. If you don't use autoincrement, then SQLite assigns a rowid that is one higher than the current max rowid in use. Hi Glenn, as I understand it, autoincrement always chooses a number that is one higher than the highest rowid ever used in the database. Your code works as expected in that I see the change of value in `sqlite_sequence`.`seq`, but the autoincrement of the database stubbornly refuses to update! ![]()
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