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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
    

table12

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

table1
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

 

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.



This article is attributed to GeeksforGeeks.org

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