SQL | Aliases

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

• 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

 

• 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.

• 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

 

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