How to add not null column to table in sql?

ALTER TABLE <Table name>
ADD <Column name>  <datatype> NOT NULL DEFAULT <default value>

How to alter a not null column to null column in sql?

ALTER TABLE <Table name>  ALTER COLUMN  <Column name>  <datatype> NULL

How to alter a null column to not null column in sql?

ALTER TABLE <Table name>
ALTER COLUMN <Column name>  <datatype> NOT NULL

SQL query for find the difference between two tables data

USE [ERM_CUSTOM]

GO

/****** Object:  StoredProcedure [dbo].[ERM_MSP_ ResourceCompareAndUpdate]    Script Date: 8/17/2016 7:52:02 AM ******/

SET ANSI_NULLS ON

GO

SET QUOTED_IDENTIFIER ON

GO

-- Exec  [dbo].[ERM_MSP_ ResourceCompareAndUpdate]

ALTER PROCEDURE [dbo].[ERM_MSP_ ResourceCompareAndUpdate]  

AS

BEGIN

SELECT  ResourceUID,

        ResourceName,

        ResourceEmailAddress,

        WWID 

INTO #TempResource

FROM [ERM].[MSP_EpmResource_UserView] -- Gets all data from view and Stored on a temp table.

CREATE TABLE #TempDifferenceResource (    ResourceUID nvarchar(max), 

                                        ResourceName nvarchar(max),

                                        ResourceEmialAddrss nvarchar(max),

                                        WWID nvarchar(max)

                                    ) --- create another temp table

  

  INSERT INTO   #TempDifferenceResource

     SELECT * FROM #TempResource 

        EXCEPT

    SELECT * FROM [dbo].[ResouceCompare]  -- insert difference data to the temp table

UPDATE

    base

SET

    base.ResourceName = tempDiff.ResourceName,

    base.ResourceEmialAddrss = tempDiff.ResourceEmialAddrss ,

    base.WWID = tempDiff.WWID

FROM

    [dbo].[ResouceCompare] base

    JOIN

    #TempDifferenceResource tempDiff 

ON    base.ResourceUID=tempDiff.ResourceUID -- update existing date to base table

insert into [dbo].[ResouceCompare]

select tempDiff.ResourceUID,tempDiff.ResourceName,tempDiff.ResourceEmialAddrss,tempDiff.WWID FROM

    [dbo].[ResouceCompare] base

    JOIN

    #TempDifferenceResource tempDiff 

ON    base.ResourceUID<>tempDiff.ResourceUID -- insert new data to base table

select * from  [dbo].[ResouceCompare]

DROP TABLE #TempResource

DROP TABLE #TempDifferenceResource

END