Sunday, 15 May 2011

SQL Alias

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;
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'.
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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