In SQL queries, aliases are playing very important roles i.e you can change or give new column name in results or you can give a new name for calculated column fields like sum of xyz. Like that you can use it tables or for queries. Lets see in details-
Aliases are mainly three types:-
Syntax:
SELECT <Column name> (AS Alias)
FROM <Table name>
Example:-
Here you can see result of this query- select "Hello SQL is with no column name-
Lets define alias for this query- select 'Hello SQL' as MyAlias and see result with as defined column name-
2. Table Alias : Used for following reasons : -
Select <Column name> (AS Alias)
FROM <Table name1> (AS Alias1), <Table name2> (AS Alias2)
Example:-
Next is Table Alias so we can start with simple query with table alias-
SELECT [FirstName], [LastName]
FROM [Person].[Person] as A
3. Query Alias : Used for sub-queries with desired name-
Syntax:
Select ( Alias1). <Column name>
FROM ( Select <Column name> FROM <Table name1> ) (AS Alias1)
Example:-
Here you can give a any name to your sub query and use it in main query-
Select A.FirstName
From
(SELECT [FirstName],[LastName]
FROM [Person].[Person]) as A
So you seen here how aliases are very helpful for designing queries. If you have any question regarding same please comment. Happy Coding
Aliases are mainly three types:-
- Column alias
- Table alias
- Query alias
Syntax:
SELECT <Column name> (AS Alias)
FROM <Table name>
Example:-
Here you can see result of this query- select "Hello SQL is with no column name-
Lets define alias for this query- select 'Hello SQL' as MyAlias and see result with as defined column name-
2. Table Alias : Used for following reasons : -
- To shorten the table name
- To remove ambiguity
- Easy to understand in Joins
Select <Column name> (AS Alias)
FROM <Table name1> (AS Alias1), <Table name2> (AS Alias2)
Example:-
Next is Table Alias so we can start with simple query with table alias-
SELECT [FirstName], [LastName]
FROM [Person].[Person] as A
3. Query Alias : Used for sub-queries with desired name-
Syntax:
Select ( Alias1). <Column name>
FROM ( Select <Column name> FROM <Table name1> ) (AS Alias1)
Example:-
Here you can give a any name to your sub query and use it in main query-
Select A.FirstName
From
(SELECT [FirstName],[LastName]
FROM [Person].[Person]) as A
So you seen here how aliases are very helpful for designing queries. If you have any question regarding same please comment. Happy Coding
