What is the use for CHECK constraint in SQL?

Answer 1

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.

Answer 2

The CHECK Constraint allows you to specify a condition on a row of the table.
If the condition is True then it will allow to enter data into the table otherwise the data won't be entered into the table.

Following is an example how Check Constraint is used:

Create Table Student(
ID int, Name varchar(20),
Age int Check(Age>=18),
);

Answer 3

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.

Query:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    City varchar(255),
    CONSTRAINT CHK_Person CHECK (Age>=18 AND City='Sandnes')
);