How to use output parameters in Oracle stored procedures

Oracle stored procedure is a special PL/SQL program that combines a set of SQL statements into a repeatable execution unit for use in an application. Stored procedures can have input, output, or bidirectional parameters. This article will discuss how to use output parameters in Oracle stored procedures.

In Oracle, common uses of stored procedures include performing complex data operations, custom validation, data conversion, etc. When it comes to returning calculation results or query results to the caller, you need to use stored procedure output parameters.

1. Declare output parameters

To declare output parameters in a stored procedure, you need to use the OUT keyword, for example:

CREATE OR REPLACE PROCEDURE test_proc(out_param OUT VARCHAR2)

where "out_param" is Parameter name, VARCHAR2 is the parameter type.

2. Set the output parameter value

Next, you can set the value of the output parameter in the stored procedure, using the following statement:

out_param := '这是输出参数的值';

Note that setting The value of the output parameter must be placed in the main part of the stored procedure, for example:

CREATE OR REPLACE PROCEDURE test_proc(out_param OUT VARCHAR2) IS
BEGIN
  out_param := '这是输出参数的值';
END;

3. Calling the stored procedure

When the stored procedure has output parameters, it needs to be called When storing the procedure, specify a variable to store the output results. For example:

DECLARE
  output_value VARCHAR2(100);
BEGIN
  test_proc(output_value);
  -- 使用output_value变量的值
END;

When calling a stored procedure, you need to specify the location of the output parameter, and the type of the variable must be the same as the type of the output parameter.

4. Example of stored procedure output parameters

Look at the simple example below, we use a stored procedure to add two numbers and store the result in an output parameter:

CREATE OR REPLACE PROCEDURE add_proc(x IN NUMBER, y IN NUMBER, sum OUT NUMBER) IS
BEGIN
  sum := x + y;
END;

In the above example, we defined three parameters: x, y and sum. The first two parameters are input parameters, and sum is the output parameter. The following is an example of calling a stored procedure:

DECLARE
  result NUMBER;
BEGIN
  add_proc(4, 5, result);
  DBMS_OUTPUT.PUT_LINE('4 + 5 = ' || result);
END;

After executing the above code, the output result is: "4 5 = 9".

5. Summary

By using the output parameters of the stored procedure, the calculation results or query results can be returned to the caller, which is very useful for building large, complex applications . When declaring output parameters, you need to use the OUT keyword, set the output parameter value in the stored procedure, and when calling the stored procedure, you need to specify a variable to store the output result.

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