Aliases are the temporary names given to table or column for the purpose of a particular SQL query. It is used when name of column or table is used other than their original names, but the modified name is only temporary.

• • • Aliases are created to make table or column names more readable.
    • The renaming is just a temporary change and table name does not change in the original database.
    • Aliases are useful when table or column names are big or not very readable.
    • These are preferred when there are more than one table involved in a query.

Basic Syntax:

• For column alias:

  SELECT column as alias_name FROM table_name;
  column: fields in the table
  alias_name: temporary alias name to be used in replacement of original column name 
  table_name: name of table
  

• For table alias:

  SELECT column FROM table_name as alias_name;
  column: fields in the table 
  table_name: name of table
  alias_name: temporary alias name to be used in replacement of original table name
  

Queries for illustrating column alias

1. 1. 1. • To fetch ROLL_NO from Student table using CODE as alias name.

           SELECT ROLL_NO AS CODE FROM Student; 
           

           Output:

           CODE
           1
           2
           3
           4

1. 1. • To fetch Branch using Stream as alias name and Grade as CGPA from table Student_Details.

        SELECT Branch AS Stream,Grade as CGPA FROM Student_Details; 
        

        Output:

        Stream	CGPA
        Information Technology	O
        Computer Science	E
        Computer Science	O
        Mechanical Engineering	A

Queries for illustrating table alias

Generally table aliases are used to fetch the data from more than just single table and connect them through the field relations.

1. 1. 1. • To fetch Grade and NAME of Student with Age = 20.

           SELECT s.NAME, d.Grade FROM Student AS s, Student_Details
           AS d WHERE s.Age=20 AND s.ROLL_NO=d.ROLL_NO; 
           

           Output:

           NAME	Grade
           SUJIT	O