And if you want to ensure that the value inserted in one of them must exist in the other table’s column, then you should use a “Foreign key Constraint” on the column in common.
While working with multiple tables, when there are two tables that relate to each other with one column in common. The SQLite foreign key is a constraint that verifies the existence of value present in one table to another table that has a relation with the first table where the foreign key is defined. You can’t insert a value less than 10 in the “Quantity” column. Quantity INTEGER NOT NULL CHECK(Quantity > 10) SQLite check constraint a condition to check an inserted value, if the value doesn’t match the condition, it won’t be inserted. Note that, this applies on the values of the column “EmployeeId” only. This will enforce the “EmployeeId” value to be unique, no duplicated values will be allowed. SQLite Unique constraint it will prevent duplicate values among all the values of the column.įor example: EmployeeId INTEGER NOT NULL UNIQUE
If you write an insert statement, and you didn’t specify any value for that column, the column will have the value 0. SQLite Default constraint if you don’t insert any value in a column, the default value will be inserted instead.įor Example: ColumnName INTEGER DEFAULT 0 SQLite Not null constraint prevents a column from having a null value:ĬolumnName INTEGER NOT NULL DEFAULT Constraint To create a combination of columns as a primary key:.There are a lot of different ways to define a primary key on a table like: The primary key can be applied to only one column or on a combination of columns, in the latter case, the combination of the columns’ values should be unique for all the tables’ rows. SQLite Primary KeyĪll the values on a primary key column should be unique and not null Columns constraints are defined when creating a table, in the column definition. Column constraints enforce constraints and rules to the values inserted on a column in order to validate the inserted data.
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