SQL -Structured Query Language - Sql Clause - As or Alias Tutorial

To create a short name for a long column or table name temporarily. Then we can use an ' AS ' statement or Alias.

This is mainly used in joins,i.e when using two tables. Suppose the two tables have the same column name ( for e.g id), then it can easy to identify if Alias is used with the column name.

Syntax-

The basic syntax of the AS statement is.–

SELECT short_name.id,short_name.name 
FROM 
table_name AS short_name;

Syntax using (inner joins)-

SELECT * FROM 
table_name1 AS short_name1 
inner join 
table_name2 AS short_name2 
WHERE 
short_name1.col_name =  short_name2.col_name;

For example( using inner join) -

SELECT e.employee_id,e.first_name,e.email,jh.start_date,jh.end_date 
FROM 
employees AS e 
inner join 
job_history AS jh 
WHERE 
e.employee_id = jh.employee_id;

Run Query

If two table has the same column such as employee_id, then the alias is very useful to identify column have the same name. Because every time we cannot use the long name to use to identify columns having the same name. Hence we use an alias.

We can also Alias Column Name not only Table.