What is the purpose of the SQL TOP statement?

The TOP statement in SQL is used to select a specified number of records from a query result. It can limit the size of the result set returned, typically used in conjunction with the SELECT statement. The TOP statement allows you to specify the number of records to be returned, which can be a specific number or an expression.

The main functions of the TOP statement are as follows:

1. Limiting results set size: The TOP statement allows you to specify the number of records to return, thereby limiting the size of the query result set. For example, you can use TOP 10 to retrieve the first 10 records in the query result.
2. Sort the result set: The TOP statement can be combined with the ORDER BY clause to sort the result set based on specific columns. By using TOP and ORDER BY together, you can obtain the top N records after sorting.
3. Improve query performance: When dealing with large datasets, using the TOP statement can decrease the execution time and resource consumption of queries. By limiting the number of records returned, the workload on the server when returning result sets can be reduced.

In summary, the purpose of the TOP clause is to select the top N records from the query results, in order to manipulate the result set size limitations, sort the result set, or improve query performance.