The GROUP BY clause partitions the resultset into one or more subsets. Each subset has values and expressions in common
s from two different query statements can be combined into a single resultset using the UNION operator.
The ALTER TABLE statement is used to modify a table definition / structure by altering, adding, or dropping columns and constraints.
In order to tell the SQL Server what actions to perform whenever a user trying to delete or update a primary key value to which existing foreign key points, we are provided with the following options while working with Cascading Referential Integrity Constraints.