When it comes to executing dynamic SQL statements in SQL Server, developers often have to choose between using the sp_executesql stored procedure or the EXECUTE statement. Both options have their own set of properties and considerations that can impact performance and security.

Common Properties of SP_EXECUTESQL and EXECUTE/EXEC

One common property of both sp_executesql and EXECUTE/EXEC is that the Transact-SQL statements in the executed string are not compiled into an execution plan until the execution occurs. This means that the strings are not parsed or checked for errors until they are executed.

Another property is that the names referenced in the strings are not resolved until they are executed. Additionally, the Transact-SQL statements in the executed string do not have access to any variables declared in the batch that contains the sp_executesql or EXECUTE statement. Similarly, the batch containing the sp_executesql or EXECUTE statement does not have access to variables or local cursors defined in the executed string.

Advantages of SP_EXECUTESQL

One major advantage of using sp_executesql over the EXECUTE statement is the ability to use parameterized statements. Parameterized statements not only eliminate the risk of SQL injection but also provide the advantage of cached query plans.

The sp_executesql stored procedure supports parameters, making it a more secure option. By using sp_executesql instead of the EXECUTE statement, you can improve the readability of your code, especially when there are many parameters involved.

Furthermore, when you use sp_executesql to execute a Transact-SQL statement that will be reused multiple times, the SQL Server query optimizer will reuse the execution plan generated for the first execution, as long as the only variation is the change in parameter values. This can significantly improve performance.

Additionally, sp_executesql can be used instead of stored procedures to execute a Transact-SQL statement multiple times when the only variation is the change in parameter values. Since the Transact-SQL statement itself remains constant and only the parameter values change, the SQL Server query optimizer is likely to reuse the execution plan generated for the first execution.

Performance and Security Considerations

It is recommended to use SP_EXECUTESQL rather than EXECUTE/EXEC due to its better performance and improved security. By utilizing parameterized statements, you can prevent SQL injection attacks and take advantage of cached query plans.

The syntax for sp_executesql in SQL Server 2005 is as follows:

sp_executesql [ @stmt = ] stmt 
[ {, [@params=] N'@parameter_name data_type [ OUT | OUTPUT ][,...n]' } 
{ , [ @param1 = ] 'value1' [ ,...n ] } ]

The size of the string is limited only by the available database server memory. On 64-bit servers, the size of the string is limited to 2 GB, which is the maximum size of nvarchar(max).

By understanding the properties and advantages of sp_executesql and its ability to improve performance and security, developers can make informed decisions when executing dynamic SQL statements in SQL Server.