SQL Server AS keyword

The AS keyword is used to assign an alias name of a column or a table

Syntax:

SELECT COL1, COL1 
    FROM Table_Name AS DEMO

-- CREATE TABLE
CREATE TABLE [dbo].[Tbl_Demo](
    [ID] [int] IDENTITY(1,1) NOT NULL,
    [Name] [varchar](500) NULL,
    [Age] [int] NULL,
    [IsActive] [bit] NULL,
    [IsDeleted] [bit] NULL,
 CONSTRAINT [PK_Tbl_Demo] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF
GO
--INSERT TABLE ROWS
SET IDENTITY_INSERT [dbo].[Tbl_Demo] ON 

GO
INSERT [dbo].[Tbl_Demo] ([ID], [Name], [Age], [IsActive], [IsDeleted]) VALUES (1, N'Anil Singh', 30, 1, 0)
GO
INSERT [dbo].[Tbl_Demo] ([ID], [Name], [Age], [IsActive], [IsDeleted]) VALUES (2, N'Aradhya', 3, 1, 0)
GO
INSERT [dbo].[Tbl_Demo] ([ID], [Name], [Age], [IsActive], [IsDeleted]) VALUES (3, N'Reena', 28, 1, 0)
GO
INSERT [dbo].[Tbl_Demo] ([ID], [Name], [Age], [IsActive], [IsDeleted]) VALUES (4, N'Sunil Singh', 27, 1, 0)
GO
INSERT [dbo].[Tbl_Demo] ([ID], [Name], [Age], [IsActive], [IsDeleted]) VALUES (5, N'Sushil', 22, 1, 0)
GO
SET IDENTITY_INSERT [dbo].[Tbl_Demo] OFF
GO

-- SELECT TABLE ROWS
SELECT * FROM [dbo].[Tbl_Demo] AS DEMO

-- Result looks like,
ID  Name    Age IsActive    IsDeleted
--------------------------------------------
1   Anil Singh  30  1   0
2   Aradhya 3   1   0
3   Reena   28  1   0
4   Sunil Singh 27  1   0
5   Sushil  22  1   0