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