How to call stored procedure in Oracle

Oracle is a very popular relational database management system that supports the use of stored procedures to implement complex business logic. A stored procedure is a piece of precompiled code saved in the database that can be called to perform a series of operations, thereby simplifying code complexity and improving efficiency. In this article, we will discuss how to call stored procedures in Oracle.

1. Define stored procedures

First, we need to define a stored procedure in the database. Stored procedures can be written using PL/SQL or SQL language. In PL/SQL, the basic syntax of stored procedures is as follows:

CREATE [OR REPLACE] PROCEDURE procedure_name
    [ (parameter_name [IN | OUT | IN OUT] type [, ...]) ]
IS
    [declaration_section]
BEGIN
    executable_section
[EXCEPTION
    exception_section]
END [procedure_name];

Among them, procedure_name is the name of the stored procedure, parameter_name is the parameter name of the stored procedure, type is the data type of the parameter, declaration_section is the declaration part, and executable_section is the executable part, and exception_section is the exception handling part.

For example, the following is a simple stored procedure, which is used to query employees' personal information based on employee IDs in the employees table:

CREATE OR REPLACE PROCEDURE get_employee_info
    (employee_id IN NUMBER, 
    name OUT VARCHAR2,
    email OUT VARCHAR2)
IS
BEGIN
    SELECT first_name || ' ' || last_name, email INTO name, email
    FROM employees
    WHERE employee_id = get_employee_info.employee_id;
END;

In this stored procedure, we define three Parameters: employee_id is the input parameter, name and email are the output parameters. In the executable part, we use a SELECT statement to get the employee's name and email from the employees table and then store them in the output parameters.

2. Calling stored procedures

Once we define a stored procedure, we can call it in other programs. There are several ways to call stored procedures, including using SQL Developer, PL/SQL Developer, or the command line interface.

In SQL Developer, you can use the following syntax to call a stored procedure:

DECLARE
    variable_name1 datatype;
    variable_name2 datatype;
BEGIN
    procedure_name(parameter_value1, parameter_value2, ..., parameter_valueN);
    variable_name1 := parameter_valueX;
    variable_name2 := parameter_valueY;
END;

Among them, variable_name is the variable used to store the output parameter value, datatype is the data type, and parameter_value is the input parameter. value, parameter_valueX and parameter_valueY are the values ​​stored in the output parameters.

For example, we can use the following command to call the above get_employee_info stored procedure:

DECLARE
    name VARCHAR2(30);
    email VARCHAR2(50);
BEGIN
    get_employee_info(100, name, email);
    DBMS_OUTPUT.PUT_LINE('Name: ' || name);
    DBMS_OUTPUT.PUT_LINE('Email: ' || email);
END;

In this example, we use the DBMS_OUTPUT.PUT_LINE statement in the executable part to print the value of the output parameter.

In addition, in PL/SQL Developer, you can use the following syntax to call stored procedures:

VARIABLE variable_name1 datatype;
VARIABLE variable_name2 datatype;
EXECUTE procedure_name(parameter_value1, parameter_value2, ..., parameter_valueN);
PRINT variable_name1;
PRINT variable_name2;

In the command line interface, you can use the following SQL statements to call stored procedures:

BEGIN
    procedure_name(parameter_value1, parameter_value2, ..., parameter_valueN);
END;

3. Advantages of stored procedures

One of the main advantages of using stored procedures is to reduce the complexity of the code. Stored procedures can encapsulate complex logic into a single unit, simplifying code writing and maintenance. Additionally, stored procedures can improve performance because they are precompiled, allowing for faster execution across multiple executions.

In addition, stored procedures also provide a certain degree of security. Stored procedures can run on the database server rather than on the client, which means the code for the stored procedure is not transmitted over the network to the client and no sensitive information is exposed.

In short, stored procedures are a very useful feature in Oracle that can improve the performance and security of database applications to a certain extent. We can call stored procedures through the above methods and use them in future tasks to perform complex operations.

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