Once the table is created in SQL Server, you can modify the table structure either through GUI or through script. I am going to list down the possible cases of updating the table structure
Add a column:
ALTER TABLE "TABLE-NAME" ADD "COLUMN-NAME" varchar(50) NULL
Modify the Data Type:
ALTER TABLE "TABLE-NAME" ALTER COLUMN "COLUMN-NAME" "NEW DATA TYPE" NULL
Modify the NOT-NULL Constraint:
ALTER TABLE "TABLE-NAME" ALTER COLUMN "COLUMN-NAME" VARCHAR(30) NOT NULL
