SQL Alias – AS Keyword

What is an Alias?

• An SQL alias is simply an alternative name that can be used to refer to a table or column within a SQL query.
• This is especially useful for large or complex queries.
• Alias is primarily used to provide a short alias name for a complexly named column or table.
• The AS keyword is used to create an alias for a table or column.

Syntax:

• Table Alias

SELECT column1, column2....
FROM table_name AS alias_name
WHERE [condition];

• Column Alias

SELECT column_name AS alias_name
FROM table_name
WHERE [condition];

Example of Alias:

Consider the following Student table:

ID	Name	Marks
1	John	64.12
2	Sam	72.50
3	Alan	45.90
4	Rabecca	86.37
5	Anjali	92.01

and Address_S table:

ID	Address
1	DELHI
2	MUMBAI
3	CHENNAI
4	NOIDA
5	PANIPAT

Query to fetch data from both tables using SQL Alias(Table Alias):

 SELECT S.ID, S.NAME, S.MARKS, A.ADDRESS 
   FROM STudent AS S, ADDRESS_S AS A
   WHERE  S.ID = A.ID;

Output:

ID	Name	Marks	Address
1	John	64.12	DELHI
2	Sam	72.50	MUMBAI
3	Alan	45.90	CHENNAI
4	Rabecca	86.37	NOIDA
5	Anjali	92.01	PANIPAT

Query for Column Alias:

SELECT  ID AS STUDENT_ID, NAME AS STUDENT_NAME
   FROM STUDENT
   WHERE MARKS > 80;

Output:

STUDENT_ID	STUDENT_Name
4	Rabecca
5	Anjali

Note: also read about SQL Functions-II

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