apache derby procedures

In Apache Derby, a procedure is a set of SQL statements that are executed as a single unit. Procedures can be used to simplify complex tasks, improve code reuse, and improve performance by reducing the amount of data that needs to be transferred between the database server and client.

Here is the basic syntax of creating a procedure in Apache Derby:

CREATE PROCEDURE procedure_name ([IN | OUT | INOUT] parameter_name data_type [, ...])
LANGUAGE JAVA
EXTERNAL NAME 'java_class_name.method_name'
[PARAMETER STYLE JAVA | DERBY JDBC]
[NO SQL | READS SQL DATA | MODIFIES SQL DATA]

In this syntax, procedure_name is the name of the procedure, parameter_name is the name of a parameter passed to the procedure, data_type is the data type of the parameter, java_class_name is the fully-qualified name of the Java class that contains the method to be called, method_name is the name of the method to be called, and PARAMETER STYLE, NO SQL, READS SQL DATA, and MODIFIES SQL DATA are optional clauses that specify how the procedure interacts with the database.

Here is an example of creating a simple procedure in Apache Derby:

CREATE PROCEDURE get_student_by_id (IN student_id INT, OUT student_name VARCHAR(50))
LANGUAGE JAVA
EXTERNAL NAME 'com.example.StudentDao.getStudentById'
PARAMETER STYLE JAVA
READS SQL DATA

In this example, the procedure is called get_student_by_id. It takes an integer parameter named student_id as input and a string parameter named student_name as output. The procedure is implemented in the com.example.StudentDao Java class, which has a method named getStudentById that takes an integer parameter and returns a string. The PARAMETER STYLE JAVA clause specifies that the parameters are passed to the Java method as Java objects, and the READS SQL DATA clause specifies that the procedure only reads data from the database.

Once a procedure is created, you can call it from an SQL statement using the CALL statement. Here is an example of calling the get_student_by_id procedure:

CALL get_student_by_id(1, ?);

In this example, the get_student_by_id procedure is called with an input value of 1 for the student_id parameter, and an output value is returned for the student_name parameter.

Procedures can be a powerful tool for simplifying complex database operations and improving performance. However, it's important to use them judiciously and to carefully consider the performance trade-offs of using procedures versus using plain SQL statements. It's also important to properly secure your procedures to prevent unauthorized access and to avoid SQL injection attacks.