![]() However, PostgreSQL returned the following error message: ERROR: new row for relation "employees" violates check constraint "employees_salary_check"ĭETAIL: Failing row contains (1, John, Doe,, , -100000). The statement attempted to insert a negative salary into the salary column. VALUES ( 'John', 'Doe', '', '', - 100000) Code language: SQL (Structured Query Language) ( sql ) ![]() Let’s try to insert a new row into the employees table: INSERT INTO employees (first_name, last_name, birth_date, joined_date, salary) Third, the salary must be greater than zero, which is obvious.This check will prevent from updating invalid dates in terms of their semantic meanings. Second, the joined date ( joined_date) must be greater than the birth date ( birth_date).If you try to insert a birth date before, you will receive an error message. First, the birth date ( birth_date) of the employee must be greater than.The employees table has three CHECK constraints: ) Code language: SQL (Structured Query Language) ( sql ) Joined_date DATE CHECK (joined_date > birth_date), The following statement defines an employees table. Typically, you use the CHECK constraint at the time of creating the table using the CREATE TABLE statement. Define PostgreSQL CHECK constraint for new tables Otherwise, PostgreSQL will reject the changes and issue a constraint violation error. If the values pass the check, PostgreSQL will insert or update these values to the column. The CHECK constraint uses a Boolean expression to evaluate the values before they are inserted or updated to the column. Summary: in this tutorial, you will learn about the PostgreSQL CHECK constraints and how to use them to constrain values in columns of a table based on a boolean expression.Ī CHECK constraint is a kind of constraint that allows you to specify if values in a column must meet a specific requirement.
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