SQL CHECK Constraint

## SQL Basic

SQL HOME SQL Intro SQL Syntax SQL SELECT SQL SELECT DISTINCT SQL WHERE SQL AND & OR SQL ORDER BY SQL INSERT INTO SQL UPDATE SQL DELETE SQL Injection

## SQL Advanced

SQL SELECT TOP SQL LIKE SQL Wildcards SQL IN SQL BETWEEN SQL Aliases SQL Joins SQL INNER JOIN SQL LEFT JOIN SQL RIGHT JOIN SQL FULL JOIN SQL UNION SQL SELECT INTO SQL INSERT INTO SELECT SQL CREATE DB SQL CREATE TABLE SQL Constraints SQL NOT NULL SQL UNIQUE SQL PRIMARY KEY SQL FOREIGN KEY SQL CHECK SQL DEFAULT SQL CREATE INDEX SQL DROP SQL ALTER SQL Auto Increment SQL Views SQL Dates SQL NULL Values SQL NULL Functions SQL General Data Types SQL DB Data Types

## SQL Functions

SQL Functions SQL AVG() SQL COUNT() SQL FIRST() SQL LAST() SQL MAX() SQL MIN() SQL SUM() SQL GROUP BY SQL HAVING SQL UCASE() SQL LCASE() SQL MID() SQL LEN() SQL ROUND() SQL NOW() SQL FORMAT()
SQL Quick Ref SQL Hosting SQL Summary

## SQL Quiz

SQL Quiz

# SQL CHECK Constraint

« Previous
Next Chapter »

## SQL CHECK Constraint

The CHECK constraint is used to limit the value range that can be placed in a column.

If you define a CHECK constraint on a single column it allows only certain values for this column.

If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row.

## SQL CHECK Constraint on CREATE TABLE

The following SQL creates a CHECK constraint on the "P_Id" column when the "Persons" table is created. The CHECK constraint specifies that the column "P_Id" must only include integers greater than 0.

MySQL:

CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CHECK (P_Id>0)
)

SQL Server / Oracle / MS Access:

CREATE TABLE Persons
(
P_Id int NOT NULL CHECK (P_Id>0),
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')
)

## SQL CHECK Constraint on ALTER TABLE

To create a CHECK constraint on the "P_Id" column when the table is already created, use the following SQL:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CHECK (P_Id>0)

To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')

## To DROP a CHECK Constraint

To drop a CHECK constraint, use the following SQL:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT chk_Person

MySQL:

ALTER TABLE Persons
DROP CHECK chk_Person
« Previous
Next Chapter »

## Your suggestion:

Your E-mail (optional):

Page address:

Description:

Close [X]

## Thank You For Helping Us!

Your message has been sent to W3Schools.

Close [X]
Search w3schools.com:

## WEB HOSTING

Best Web Hosting UK Reseller Hosting Wow! $5 SSD Hosting

## WEB BUILDING

Download XML Editor
FREE Website BUILDER FREE Website Creator

## WEB RESOURCES

Web Statistics Web Validation

## SHARE THIS PAGE