If I adjust the discount so that it’s lower than the price, it’s inserted successfully. Here’s what happens if I try to insert a discount that’s larger than the price. This table is similar to the first one, except that I’ve added an extra column called Discount.įor the CHECK constraint, I’m now checking that the price is larger than the discount (we don’t want the possibility of having a discount that’s larger than the actual price). Here’s an example of a table-level CHECK constraint. The default setting is off, meaning that CHECK constraints are enforced by default. This pragma statement explicitly enables or disables the enforcement of CHECK constraints. In other words, you can use a table-level constraint to check data from multiple columns. check (id < 10)) sqlite> insert into test values (1) Error: stepping, CHECK constraint failed: id > 1 (19) sqlite>. If you ever need to enable or disable all CHECK constraints in SQLite, you can use the ignorecheckconstraints PRAGMA statement. IMO the simplest and most easily expandable solution: CHECK (status IN ('Current', 'Complete')) CHECK (status <> 'Complete' OR enddate IS NOT NULL) This uses the fact that if A then B is logically equivalent to either not A or B.INSERT INTO Products VALUESġ Blue Widget 1.0 Table-Level CHECK ConstraintĪ table-level CHECK constraint checks data across the whole row, rather than just a single column. There's nothing stopping you from having multiple CHECK constraints on a single table. INSERT INTO Products VALUESīut if I increase it to a value that’s greater than zero, then the INSERT operation succeeds. I get the same result if I try to use a negative value. Result: Error: CHECK constraint failed: Products Now let’s see what happens if we try to insert data that violates this constraint. In this case, it specifies that the price must be greater than zero. The part that goes CHECK (Price > 0) is the CHECK constraint. Here’s an example of creating a column-level CHECK constraint. If a table has a CHECK constraint on it, and you try to insert or update data that violates the CHECK constraint, the operation will fail with an error. Many constraints are available in the SQL database, i.e., Primary key, Unique Key, Foreign key, Composite check, WHERE clauses, and many more. In SQLite, you can create a CHECK constraint by adding the applicable code within the CREATE TABLE statement when creating the table.
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