- Tags: Keyword, MySQL, SQL Server
- Categories: Reference, SQL Keywords, SQL Reference
Quick Reference
The CHECK keyword is a constraint that limits the value that can be placed in a column.
SQL CHECK on CREATE TABLE
The following creates a CHECK constraint on the user_age column when the Users table is created. The CHECK constraint ensures that you can not have any person less than 18 years of age.
MySQL:
CREATE TABLE Users (
user_age int,
CHECK (user_age >= 18)
);
SQL Server:
CREATE TABLE Users (
user_age int CHECK (user_age >= 18)
);
SQL CHECK on ALTER TABLE
The following creates a CHECK constraint on the user_age column on an existing table. In the SQL Server version, the constraint is named check_age.
MySQL:
ALTER TABLE Users
ADD CHECK (user_age >= 18);
SQL Server:
ALTER TABLE Users
ADD CONSTRAINT check_age CHECK (user_age >= 18);
We’d like to acknowledge that we learned a great deal of our coding from W3Schools and TutorialsPoint, borrowing heavily from their teaching process and excellent code examples. We highly recommend both sites to deepen your experience, and further your coding journey. We’re just hitting the basics here at 1SMARTchicken.
Why 1SMARTchicken?
See More →
Thanks for your support!
SQL Books
All are affiliate links. Thank you for your support!
SQL NOTES:
- Any work being done to modify the structure of a database or delete tables or the the database itself should only be done after making a recent backup
Feedback
If you see an error on the page or the code itself is incorrect or incomplete, or just plain wrong, please let us know. We’re always learning. NOTE: we do not sell your information and will not send you spam emails.
