for table columns, indexes, foreign keys, triggers, unique and check constraints.
You will first start querying data from the sample database. Advanced SQL editor with syntax highlighting and code completion.
If the values do not meet the criteria defined by the expression, SQLite will issue a constraint violation and abort the statement. This section presents basic SQL statements that you can use with SQLite. SQLite CHECK constraints allow you to define expressions to test values whenever they are inserted into or updated within a column.
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): Following is the syntax, ALTER TABLE tablename ADD ( columnname datatype) Here is an Example for this, ALTER TABLE student ADD ( address VARCHAR (200) ) The above command will add a new column address to the table student, which will hold data of. The syntax to add a foreign key to an existing table in SQLite is: PRAGMA foreign_keys=off ĪLTER TABLE table1 RENAME TO _table1_old Using ALTER command we can add a column to any existing table. 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 in SQLite. How to Add a Foreign Key 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. 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 using the CREATE TABLE statement in SQLite. REFERENCES parent_table (column1, column2. The syntax to create a foreign key using a CREATE TABLE statement in SQLite is: CREATE TABLE table_nameįOREIGN KEY (column1, column2. CREATE TABLE tablename (col1 INTEGER PRIMARY KEY, col2 TEXT NOT NULL, col3 INTEGER CHECK (col3 > 0)) If you observe above syntax we added Check Constraint for column col3 to allow only values which are greater than zero (0). How to Create a Foreign Key using the CREATE TABLE Statement Syntax Syntax of SQLite Check Constraint Following is the syntax of adding check constraint on table column.