Database Constraints

Database Constraints

Constraints are the rules which are applied to a table to filter out data during insert or update operations. Constraints can be added at the time of creating a table or altering a table. Constraints are the conditions which should be satisfied by insert or update query. There are 2 types of constraints:

1)      Input output (I/O) constraints:

a.       These are of following types:

                                                               i.      Primary Key

                                                             ii.      Foreign Key

                                                            iii.      Unique Key

2)      Check (Business Rules) constraints:

a.       These are defined at 2 levels

                                                               i.      Table Level

                                                             ii.      Column Level

List of SQL Queries

SQL Queries

Table Structure Related Queries:

1)      Create table

2)      Rename a table

3)      Creating a table from another table

4)      Deleting a table

5)      Adding a new column in an existing table

6)      Modifying a column in an existing table

7)      Deleting a column from an existing table

8)      Adding Primary Key during creating a table

9)      Adding Primary Key in an existing table

10)   Adding Foreign Key during creating a table

11)   Adding Foreign Key in an existing table

12)   Dropping a Primary Key from a table

13)   Dropping a Foreign Key from a table

14)   Defining Check constraint at Column Level while creating a table

15)   Defining Check constraint at Column Level using alter table

16)   Defining Check constraint at Table Level while creating a table

17)   Defining Check constraint at Table Level using alter table

18)   Dropping a Check constraint

Working with Table:

1)      Insert values in the table

2)      Update values in the table

3)      Delete values in the table

4)      Truncate Table (To empty a table- to delete all records)

5)      Selecting values from table

6)      Where Clause

7)      Desc (Description)

8)      Order BY Clause

9)      Group By Clause

10)   Having Clause

11)   Distinct Clause

12)   Searching Record using: Between, IN, NOT IN, Like

13)   Oracle Functions: AVG (), MIN (), MAX (), COUNT (), SUM (), SQRT (), EXP (), MOD (), TRUNC (), FLOOR (), CEIL (), LOWER (), UPPER (), ASCII ().

Sub Queries:

1)      Finding Duplicate Records from a Table

2)      Deleting Duplicate Records from a Table

3)      Finding Highest Salary from Employee Table

4)      Finding 2^nd Highest Salary from Employee Table

5)      Finding 5^th Highest Salary from Employee Table

6)      Finding N^th    Highest Salary from Employee Table

Database Objects:

1)      Creating View

2)      Deleting View

3)      Creating Join

4)      Create Index

6)      Delete Index