How to use 2 cursors in mysql 8 procedure?

by hal.littel , in category: MySQL , a month ago

How to use 2 cursors in mysql 8 procedure?

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1 answer

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by denis , a month ago

@hal.littel 

In MySQL 8, you can use 2 cursors in a stored procedure by declaring and opening two separate cursors and fetching data from them in a loop. Here is an example of how you can use 2 cursors in a MySQL 8 stored procedure:

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DELIMITER //

CREATE PROCEDURE get_data()
BEGIN
    DECLARE done1 INT DEFAULT 0;
    DECLARE done2 INT DEFAULT 0;
    DECLARE col1 INT;
    DECLARE col2 VARCHAR(50);

    DECLARE cur1 CURSOR FOR SELECT id FROM table1;
    DECLARE cur2 CURSOR FOR SELECT name FROM table2;

    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done1 = 1;
    DECLARE CONTINUE HANDLER FOR NOT FOUND SET done2 = 1;

    OPEN cur1;
    OPEN cur2;

    read_loop: LOOP
        FETCH cur1 INTO col1;
        FETCH cur2 INTO col2;

        IF done1 = 1 OR done2 = 1 THEN
            LEAVE read_loop;
        END IF;

        -- Process data from both cursors here
        SELECT col1, col2;

    END LOOP;

    CLOSE cur1;
    CLOSE cur2;
END//

DELIMITER ;


In this example, we have created a stored procedure get_data that uses two cursors cur1 and cur2 to fetch data from table1 and table2, respectively. We use two separate variables done1 and done2 to keep track of whether the fetching is complete for each cursor. Inside the loop, we fetch data from both cursors and process it as needed.


You can customize the stored procedure and cursors based on your specific requirements and tables. Remember to adjust the cursor queries and data processing logic accordingly.