If you find that you are issuing a statement over and over again, the database will be doing a lot of work that can be avoided. The way to do this is with a prepared statement. As the name implies, the prepared statement is constructed and sent to the SQL interpreter. The output of the interpreter (the native code instructions) is then saved. The prepared statement can later be reissued, perhaps with different parameters, and it will run much more quickly because the interpretation step has already been done. Does this remind you of anything? This is exactly how Just-In-Time (JIT) Java compilers speed up execution—by compiling to native code and caching the results.

A stored procedure is a similar idea to prepared statements but taken one step further. Instead of caching an individual statement, you can save a whole series of statements as a procedure. A stored procedure will typically implement one entire operation on a database, like adding an employee to all the relevant tables (payroll, department, benefits, social club, etc.). It is typical to provide parameters to a stored procedure; for example, giving the details of the employee who is being added to the company.

The vast majority of database systems support stored procedures, but a major sticking point has been the variation in the exact syntax used. JDBC 2 solves this issue by allowing you to write stored procedures in Java. That means your library of stored procedures is now portable to all databases, which is a major step forward!

This concludes our tour of the concepts of SQL and databases, and we now proceed to Chapter 24 to look at how you put it all together in Java.