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Check in DBMS
In this article, we will learn about Check-in DBMS.
- Suppose in real-time if you want to give access to an application only if the age entered by the user is greater than 18 this is done at the back-end by using a
check
constraint - Check constraint ensures that the data entered by the user for that column is within the range of values or possible values specified.
Syntax for check constraint
CREATE TABLE STUDENT (
column1 datatype(size),
column2 datatype(size),
column3 datatype(size),
CHECK (condition)
);


Example for check constraint
CREATE TABLE STUDENT (
ID int ,
Name varchar(255) ,
Age int,
CHECK (Age>=18)
);
- As we have used a check constraint as (Age>=18) which means values entered by the user for this age column while inserting the data must be less than or equal to 18 otherwise an error is shown
- Simply, the only possible values that the age column will accept is [0 -17].
Check constraint at table level
CREATE TABLE student {
ID int ,
Name varchar(255) ,
Program interface specificationAge int,
City varchar(255),
CONSTRAINT CHK_Person CHECK (Age>=18 AND City='hyderabad')
);
- You can apply check constraint to more than one column at a time
- In the above example we have used two conditions with the check constraint Age>=18 AND City=’ Hyderabad’ , as a result, both the columns age and city will be checked while data is entered i.e the only possible values that are accepted for the column age are 0 -17 and city must be only Hyderabad
Learn more about DBMS here on this page.
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