How to Create Column Constraint and Table Constraint in SQL
In this article I am going to explain about Column Constraint and Table Constraint in SQL.
Introduction
In SQL you can set constraint on column or table according to need. Column constraint only applies on specific column. A table constraint is used when you want to set constraint on more than one column in a table. Table constraints must be used when you need to put more than one column into a single constraint.
Example of column Constraint
Statement that create primary key
create table empinfo
(
id int primary key,
name varchar(15),
age int,
city varchar(15),
salary money
)
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Example of Table Constraint
In this example we are creating a primary key constraint using empid and emp_panno. It is example of table constarint.
Statement that create Primary key constraint using two attribute in empinfo table
create table empinfo
(
empid int,
emp_panno int,
name varchar(15),
age int,
city varchar(15),
salary money
CHECK(salary >=10000 and salary <=1000000)
constraint p_K primary key(empid,emp_panno)
)
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