A Subquery or Inner query or a Nested query is a query within another SQL query and embedded within the WHERE clause.
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.