oracle stored procedure returns result set

Oracle is one of the most widely used relational database management systems in the world. It has the advantages of good stability, scalability and security. In addition, Oracle also provides the stored procedure function, which is a kind of function in the database. A collection of executed SQL statements whose syntax is similar to PL/SQL. Stored procedures are mainly used to simplify repetitive code, improve code reusability, speed up data processing, etc. This article will introduce how to write stored procedures in Oracle and return result sets.

1. Basics of stored procedures

In Oracle, a stored procedure is a collection of SQL statements that can perform queries, inserts, updates, deletes and other database operations. In Oracle, stored procedures can be written using PL/SQL language. A stored procedure is a database object that is created using the CREATE PROCEDURE statement. In addition, you can also use the CREATE FUNCTION statement to create a function type stored procedure. The stored procedure of function type returns a value, while the stored procedure does not return a value, but the OUT parameter can be used in it to return the result. Stored procedures allow users to customize parameters, reducing the complexity of data access and processing.

Advantages of stored procedures:

1. Reduce repetitive code
2. Reduce the burden on the database and network
3. Enhance the readability and readability of the code Maintainability
4. Improve data processing speed

Disadvantages of stored procedures:

1. Increased memory usage
2. Increased development and testing time
3. High programming complexity

2. Syntax of stored procedure

The stored procedure mainly consists of DECLARE, BEGIN, EXCEPTION and END statements, among which the DECLARE statement is used Declare variables, cursors, record types, etc. The BEGIN statement contains the main execution code of the stored procedure, which is used to implement the specific functions of the stored procedure. It can include control structures such as IF, LOOP, WHILE, etc. and SQL statements. The EXCEPTION statement is used to handle exceptions in operations. The END statement indicates the end of the stored procedure.

The syntax of the stored procedure is as follows:

CREATE OR REPLACE PROCEDURE procedure_name (IN_parameter IN data_type, OUT_parameter OUT data_type)
IS
DECLARE
variable_name data_type := value ;
BEGIN
--Execution statement
EXCEPTION
--Exception handling
END;

Parameter description:

1. CREATE OR REPLACE PROCEDURE: Create or replace stored procedures

2. procedure_name: The name of the stored procedure, which must be unique.

3. IN_parameter: The name of the input parameter of the stored procedure, which can be a single parameter or multiple parameters.

4. data_type: the data type of IN_parameter

5. OUT_parameter: the name of the output parameter of the stored procedure. Can return record or cursor type.

6. DECLARE: used to declare variables, cursors, record types, etc.

7. variable_name: the name of the variable

8. value: the assignment of the variable

9. BEGIN: contains the main execution code of the stored procedure, used to implement the stored procedure specific functions.

10. EXCEPTION: Used to handle exceptions during operations.

11. END: The stored procedure ends.

3. The stored procedure returns the result set

In Oracle, the stored procedure can return the results through the OUT parameter. In the stored procedure, we need to use the cursor variable to read the query result set, and then pass the result to the OUT parameter. The specific steps are as follows:

1. Define the stored procedure and OUT parameters

CREATE OR REPLACE PROCEDURE procedure_name(p_out_parameter OUT SYS_REFCURSOR)
IS
BEGIN
--Execute Statement
OPEN p_out_parameter FOR SELECT column1, column2 FROM table_name;
END;

Explanation:

The above stored procedure defines an OUT parameter p_out_parameter, the data type of this parameter is SYS_REFCURSOR .

2. Call stored procedure

DECLARE
type_name SYS_REFCURSOR;
BEGIN
procedure_name(type_name);
END;

Description:

Use the DECLARE keyword to define a cursor variable type_name, whose data type is SYS_REFCURSOR.

Call the stored procedure procedure_name and pass the parameter type_name to the OUT parameter p_out_parameter. After the execution of the stored procedure is completed, the returned query results will be stored in the cursor variable type_name.

3. Use cursor variables to read query results

DECLARE
type_name SYS_REFCURSOR;
column1_value VARCHAR2(50);
column2_value VARCHAR2(50);
BEGIN
procedure_name(type_name);
LOOP

FETCH type_name INTO column1_value, column2_value; 
EXIT WHEN type_name%NOTFOUND; 
--使用查询结果进行其他操作 

END LOOP;
CLOSE type_name;
END;

Instructions:

Use the above code The cursor variable type_name reads the query result set row by row and stores the column1 and column2 values ​​of each row in the variables column1_value and column2_value.

Through the LOOP and FETCH statements, the cursor variable can read the query result set row by row. When the last row is queried, the type_name%NOTFOUND condition will return TRUE and the loop will exit. Finally, use the CLOSE statement to close the cursor.

4. Summary

Stored procedures are effective data processing tools in Oracle, which can optimize data operations by reducing code duplication, improving code reusability, and speeding up data processing. When writing a stored procedure, you need to be familiar with its basic syntax and parameter rules, and understand how to return a query result set. The use of stored procedures can greatly improve the performance and security of the database, and is one of the necessary skills for Oracle database developers.

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