Saturday, 19 November 2011


SQL Alias

SQL Aliases are defined for columns and tables. Basically aliases is created to make the column selected more readable.
For Example: To select the first name of all the students, the query would be like:

Aliases for columns:

SELECT first_name AS Name FROM student_details;
or
SELECT first_name Name FROM student_details;
In the above query, the column first_name is given a alias as 'name'. So when the result is displayed the column name appears as 'Name' instead of 'first_name'.
Output:
Name
-------------
Rahul Sharma
Anjali Bhagwat
Stephen Fleming
Shekar Gowda
Priya Chandra

Aliases for tables:

SELECT s.first_name FROM student_details s; 
In the above query, alias 's' is defined for the table student_details and the column first_name is selected from the table.
Aliases is more useful when
  • There are more than one tables involved in a query,
  • Functions are used in the query,
  • The column names are big or not readable,
  • More than one columns are combined together

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