Query commands, nested and correlated queries
Query commands in SQL Server 2008 are used to retrieve data from one or more tables based on certain criteria. Some common query commands include SELECT, WHERE, GROUP BY, ORDER BY, and JOIN.
Nested queries, also known as subqueries, are queries that are embedded within other queries. The results of the nested query are used as input for the outer query. This allows for more complex queries and can be useful when you need to filter data based on the results of another query.
Correlated queries are similar to nested queries, but they are linked to the outer query by a common field or column. In other words, the nested query uses a value from the outer query to filter the results. Correlated queries can be slower than nested queries because they require more processing power, but they are useful in certain situations. Overall, query commands, nested queries, and correlated queries are all important tools in SQL Server 2008 that allow you to retrieve and manipulate data in a powerful and flexible way.
Apply for SQL Server 2008 Certification!!
https://www.vskills.in/certification/certified-sql-server-2008-programmer
