Focus on Oracle compiled stored procedures

As the amount of data in the database continues to increase, the importance of stored procedures has gradually become more prominent. The writing and use of stored procedures can improve code reusability and data query efficiency, making it easier for developers and users to operate the database. This article will focus on how to compile stored procedures.

1. Understanding stored procedures

Before we start writing stored procedures, let’s first understand the basic concepts of stored procedures. A stored procedure is a set of precompiled SQL statements that can be called and executed. Different from general SQL statements, stored procedures can provide multiple input parameters and output results, and support complex business operations on data, such as calculations, conditional judgments, loops, etc.

The advantages of stored procedures are:

1. Improve code reusability: some business logic in stored procedures can be called in multiple places, avoiding repeated entry of code.
2. Improve data query efficiency: Stored procedures can be pre-compiled, which reduces the parsing and optimization overhead of SQL statements and improves query efficiency.
3. Improve data security: The stored process can perform parameter verification and security verification, ensuring the legality and security of data operations.

2. Writing stored procedures

In Oracle database, we need to use PL/SQL language to write stored procedures. PL/SQL is a precompiled language specially designed by Oracle for objects such as stored procedures, triggers, and functions. It can be embedded in SQL statements and provides features such as block structures, loop statements, and exception handling, making stored procedure writing more convenient and efficient. flexible.

The steps to write a stored procedure are as follows:

1. Create a stored procedure

We can use the CREATE PROCEDURE statement to create a stored procedure. Its basic syntax is as follows:

CREATE [OR REPLACE] PROCEDURE Stored procedure name
Parameter declaration
IS
Program body
END Stored procedure name;

Among them, the stored procedure name is itself The name of the definition, the parameter declaration can contain input and output parameters, and the program body is the actual business logic. If you need to update an existing stored procedure, you can use the OR REPLACE keyword.

2. Writing the program body

The program body contains the actual business logic of the stored procedure. We can use IF, LOOP, WHILE and other statements to perform conditional judgments, loops and other operations, and execute SQL statements through the EXECUTE IMMEDIATE statement.

You need to pay attention to the following points when writing the program body:

(1) All statements in the program body must end with a semicolon;

(2) You can use DECLARE Declare integer variables, character variables, etc.;

(3) You can use the EXCEPTION statement to handle errors to ensure the robustness of the program.

The following is a simple stored procedure example for querying information about an employee:

CREATE OR REPLACE PROCEDURE GET_EMPLOYEE(

 EMP_ID IN NUMBER,
 EMP_NAME OUT VARCHAR2,
 EMP_SALARY OUT NUMBER)

IS
BEGIN

 SELECT EMPLOYEE_NAME, EMPLOYEE_SALARY INTO EMP_NAME, EMP_SALARY
 FROM EMPLOYEE_TABLE WHERE EMPLOYEE_ID = EMP_ID;

END GET_EMPLOYEE;

In the above example, we defined 3 parameters: an input parameter EMP_ID and two output parameters EMP_NAME and EMP_SALARY. The SELECT INTO statement is used in the program body to extract data from the employee table Query the data that meets the conditions and assign the query results to the output parameters.

3. Compile the stored procedure

After editing the stored procedure, we need to compile it to confirm its syntax Correctness and feasibility, and save it to the database. Oracle database provides two compilation methods: command line compilation and graphical compilation.

1. Command line compilation

We can use command line tools such as SQL*Plus or SQL Developer to compile stored procedures. Enter the following statement in the command line to compile:

SQL> CREATE [OR REPLACE] PROCEDURE stored procedure name

 参数声明

IS

 程序体

END Stored procedure name;

Among them, the OR REPLACE keyword can be used to replace the existing stored procedure, and the parameter declaration can include input and output parameters, etc.

2. Graphical compilation

Oracle SQL Developer is a commonly used graphical database management tool, we can use it to write and compile stored procedures.

In SQL Developer, we enter the "Procedures" tab and create a new stored procedure in it. Enter the stored procedure code in the editor and click the "Compile" button to compile it. Once If the stored procedure is compiled successfully, it will be saved in the database.

Summary:

The writing and use of stored procedures can greatly improve the efficiency of database operations. PL/SQL is the key to Oracle database A powerful, flexible, and reliable language for writing stored procedures. Writing and compiling stored procedures is a very important skill. I hope that through the introduction of this article, you can better understand stored procedures and PL/SQL language, and use them more efficiently. To implement business logic operations.

The above is the detailed content of Focus on Oracle compiled stored procedures. For more information, please follow other related articles on the PHP Chinese website!