What are stored procedures in SQL?

Stored procedures in SQL are essentially precompiled collections of SQL statements that can be executed as a single command. This means that when you create a stored procedure, you define a set of operations that the database will execute whenever the procedure is called. This process of pre-compilation improves performance, as the SQL engine does not need to parse and optimize the query every time it is run; instead, it simply executes the precompiled plan.

Using stored procedures also enhances maintainability, as you can change the logic within the procedure without affecting applications that call it. Additionally, stored procedures often allow for parameterization, making them flexible for various input values and helping to prevent SQL injection attacks.

The other options do not accurately describe stored procedures. For instance, random SQL commands executed one by one lack the structure and encapsulation that stored procedures provide. Temporary tables are distinct as they are structures for holding data temporarily and do not encapsulate SQL commands. Lastly, data stored in an unstructured format does not relate to the definition or function of stored procedures, which involve structured SQL statements.