Microsoft® SQL Server 2012 Unleashed

Recompiling Query Plans

Certain changes in a database over time can cause existing execution plans to become either inefficient or invalid, based on the new state of the database. SQL Server detects the changes that invalidate an execution plan and marks the plan as not valid. A new plan is then automatically recompiled the next time the query that uses that query plan is invoked. Most query plan recompilations are required either for statement correctness or to obtain potentially faster query execution plans. The types of conditions that can invalidate a query plan include the following:

Modifications made to the definition of a table or view ...