SQL

1. By : Dhirendra Chauahn

2. SQL constraints
• “SQL constraints are used to specify rules for the
data in a table.”
• Constraints are used to limit the type of data
that can go into a table.
• Constraints can be column level or table level.
Column level constraints apply to a column, and table
level constraints apply to the whole table.

3. Show Command
The following constraints are commonly used in SQL:
1.PRIMARY KEY
2.UNIQUE
3.NOT NULL
4.FOREIGN KEY
5.CHECK
6.DEFAULT
7.INDEX

4. PRIMARY KEY
PRIMARY KEY - A combination of a NOT NULL and
UNIQUE. Uniquely identifies each
row in a table

5. UNIQUE
UNIQUE - Ensures that all values in a column are
different

6. NOT NULL
NOT NULL - Ensures that a column cannot have a
NULL value

7. FOREIGN KEY
FOREIGN KEY - Uniquely identifies a row/record in
another table

8. CHECK
CHECK- Ensures that all values in a column satisfies
a specific condition

9. DEFAULT
DEFAULT - Sets a default value for a column when
no value is specified

10. INDEX
INDEX - Used to create and retrieve data from the
database very quickly

11. THANK
YOU