How Does a Database Engine Process Prepared Statements Compared to Normal Statements, and Why Are Prepared Statements Faster

Processing of Normal Non-Prepared Statements

Non-prepared statements, also known as direct SQL statements, involve SQL queries being written and sent to the database directly. The steps involved in processing a normal SQL statement are:

1. SQL Parsing: The database engine first parses the SQL statement to validate its syntax and structure.
2. Compilation: The parsed statement is then compiled. Compilation involves creating an execution plan that the database engine will use to execute the SQL statement.
3. Execution: The database engine then executes the SQL statement according to the execution plan.
4. Result Preparation: Finally, the engine prepares the results, which may include data retrieval or confirmation of changes made to the database.

This whole process is repeated each time a non-prepared SQL statement is executed, even if it’s the same statement.

Processing of Prepared Statements

Prepared statements are processed differently from non-prepared statements, and these differences lead to improved efficiency and speed. Here’s how:

1. SQL Parsing and Compilation: Like a normal statement, a prepared statement is parsed and compiled to create an execution plan. However, this only happens the first time the prepared statement is run.
2. Caching: The pre-compiled statement and its execution plan are stored in the database server’s cache.
3. Parameter Binding and Execution: When the prepared statement is executed, the parameter values are sent to the database and bound to the pre-compiled statement. The database engine then executes the statement according to the cached execution plan.

This process can be repeated multiple times with different parameter values, but the parsing and compilation only happen once, which significantly reduces the computational load.

Why Prepared Statements Are Faster

Prepared statements have several characteristics that make them faster and more efficient than normal statements:

1. Less CPU Usage: As prepared statements only need to be parsed, compiled, and optimized once, they require less CPU resources, which makes them faster.
2. Reduced Network Overhead: Prepared statements are sent to the server in a binary format rather than as plain text, reducing network bandwidth usage.
3. Execution Plan Reuse: The execution plan for a prepared statement is cached and reused, eliminating the need to generate a new plan for each execution.
4. Efficient Parameter Binding: Parameters in prepared statements are bound after the statement is parsed and compiled, allowing the database to execute the statement more efficiently.
5. Better Security: Prepared statements help prevent SQL injection attacks, which improves security without requiring additional computational resources.

In summary, prepared statements offer improved speed, efficiency, and security over non-prepared statements, particularly when executing the same statement multiple times with different parameters.