SELECT Statement Execution in SQL Server

SQL Server uses the following steps to process a single SELECT statement:

1. The parser breaks SELECT statement into logical units, such as keywords, expressions, operators, and identifiers.
2. A query tree is built.
3. The query optimizer then determines the best steps that can return fastest result while consuming the fewest resources.
4. The relational engine begins executing the execution plan, requesting the storage engine to pass up data.
5. The relational engine processes the data returned from the storage engine into the result set format and returns the result set to the client.