MySQL stored procedure insert multiple rows from list

Question

How can I write a MySQL stored procedure to insert values from a variable sized list? More specifically I need to insert data into one parent table, get the ID from the insert, and then insert a variable number of child records along with the new ID into another table in a one-to-many relationship. My schema looks something like this:

TableA:

table_a_id -- Auto Increment
counter
some_data...

TableB:

table_b_id -- Auto Increment
table_a_id -- Foreign Key Constraint
some_data_from_list...

My stored procedure so far looks like this:

DELIMITER ;;
CREATE PROCEDURE insert_group_alert(
  IN _some_data_a         VARCHAR(255),
  IN _data_list_b         TEXT,
)
  BEGIN
    DECLARE EXIT HANDLER FOR SQLEXCEPTION
    BEGIN
      ROLLBACK;
    END;
    START TRANSACTION;

    INSERT INTO TableA (
      some_data,
      counter
    )
    VALUES (
      _some_data_a,
      1
    )
    ON DUPLICATE KEY UPDATE
      counter          = counter + 1;

    SELECT last_insert_id()
      INTO @newId;

LIST INSERT ???:
    INSERT INTO TableB (
      table_a_id, some_data
    ) VALUES (
      @newId,
      list_item,
    );
END LIST INSERT ???

    COMMIT;
  END ;;
DELIMITER ;

My thought was to pass in a list of items to insert into table B via a comma delimited string. The values are strings. I am not sure what to do in the LIST INSERT section. Do I need a loop of some sort? Is this stored procedure I have so far the correct way to do this? I don't want to do a batch as I could potentially have hundreds or even thousands of items in the list. Is there a better solution? I am using straight JDBC.

ndsmyter · Accepted Answer · 2018-09-25 13:37:29Z

Yes, you need a loop, in which you can use substring_index() to get the values within the list. The solution is based on the answers from this SO topic:

DELIMITER ;;
CREATE PROCEDURE insert_group_alert(
  IN _some_data_a         VARCHAR(255),
  IN _data_list_b         TEXT,
)
  BEGIN
    DECLARE strLen    INT DEFAULT 0;
    DECLARE SubStrLen INT DEFAULT 0;
    DECLARE EXIT HANDLER FOR SQLEXCEPTION
    BEGIN
      ROLLBACK;
    END;
    START TRANSACTION;

    INSERT INTO TableA (
      some_data,
      counter
    )
    VALUES (
      _some_data_a,
      1
    ) -- you do not really need this, since you do not provide an id
    ON DUPLICATE KEY UPDATE
      counter          = counter + 1;

    SELECT last_insert_id()
      INTO @newId;

    do_this:
      LOOP
        SET strLen = CHAR_LENGTH(_data_list_b);

        INSERT INTO TableB (table_a_id, some_data) VALUES(@newId,SUBSTRING_INDEX(_data_list_b, ',', 1));

        SET SubStrLen = CHAR_LENGTH(SUBSTRING_INDEX(_data_list_b, ',', 1))+2;
        SET _data_list_b = MID(_data_list_b, SubStrLen, strLen); --cut the 1st list item out

        IF _data_list_b = '' THEN
          LEAVE do_this;
        END IF;
      END LOOP do_this;

    COMMIT;
  END ;;
DELIMITER ;

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