How to Split Comma-Separated Values in a MySQL Column into Separate Rows?

Mysql String Split

Problem:

You have a table with a column containing comma-separated values. You want to split these values into separate rows, with each value corresponding to a row.

For example, given the table:

Col1	col2
1	a,b,c
2	d,e

You would like to extract the following rows:

Col1	col2
1	a
1	b
1	c
2	d
2	e

Solution:

This can be achieved using a MySQL stored procedure. The following SQL script includes both the stored procedure and the function it uses:

DELIMITER $$

CREATE FUNCTION strSplit(x VARCHAR(65000), delim VARCHAR(12), pos INTEGER) 
RETURNS VARCHAR(65000)
BEGIN
  DECLARE output VARCHAR(65000);
  SET output = REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos)
                 , LENGTH(SUBSTRING_INDEX(x, delim, pos - 1)) + 1)
                 , delim
                 , '');
  IF output = '' THEN SET output = null; END IF;
  RETURN output;
END $$


CREATE PROCEDURE BadTableToGoodTable()
BEGIN
  DECLARE i INTEGER;

  SET i = 1;
  REPEAT
    INSERT INTO GoodTable (col1, col2)
      SELECT col1, strSplit(col2, ',', i) FROM BadTable
      WHERE strSplit(col2, ',', i) IS NOT NULL;
    SET i = i + 1;
    UNTIL ROW_COUNT() = 0
  END REPEAT;
END $$

DELIMITER ;

To use this stored procedure, you can run the following query:

CALL BadTableToGoodTable();

This will create a new table called 'GoodTable' with the desired data.

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