c oracle stored procedure

In Oracle database, a stored procedure is a reusable program unit that is stored in the database and can be called multiple times. Stored procedures can simplify development work, speed up execution, and improve system maintainability and scalability.

The stored procedure is composed of a set of predefined SQL statements and control statements. Used for tasks that require the execution of complex business logic. For example, an order processing application needs to perform multiple update or delete operations on the same batch of data. If you don't use stored procedures, the same SQL statement must be passed from the client application every time you process it. Using stored procedures, you can store these SQL statements in the database and execute them by calling the stored procedure.

The syntax for creating a stored procedure

The syntax for creating a stored procedure 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, parameter_name is the parameter name, type is the parameter type. Commonly used parameter types include: NUMBER, VARCHAR2, DATE, etc.

When creating a stored procedure, you need to use the IS keyword to combine parameter_name and type and other declaration parts with the actual execution part of the stored procedure separated. The actual executable section of the stored procedure is called executable_section.

Use stored procedures to implement business logic

The following is a simple example that shows how to use stored procedures to query the number of employees with a given department number:

CREATE OR REPLACE PROCEDURE count_emp (deptno IN NUMBER, cnt OUT NUMBER)
IS
BEGIN
    SELECT COUNT(*) INTO cnt FROM emp WHERE deptno = deptno_in;
EXCEPTION
    WHEN NO_DATA_FOUND THEN
        cnt := 0;
END;

The above storage The meaning of the process is to query the number of employees with the specified department number in the employee table emp by passing the department number parameter, and store the result in the output parameter cnt.

When executing a stored procedure, you can use the following statement to call it:

VAR cnt NUMBER;
EXEC count_emp(10, :cnt);
PRINT cnt;

Among them, :cnt is a bind variable, which stores the return value on the client in variable cnt.

Summary

Stored procedures are highly reusable codes in Oracle database, which can simplify development work, reduce code duplication, speed up execution and improve system maintainability and scalability. In actual applications, stored procedures can help developers effectively handle complex business logic and data structures.

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