Insert data from two table into another
Select any variant of

    INSERT INTO c (c, m)
    SELECT c.id, m.id
    FROM c, m
    WHERE c.type = 1
      AND m.type = 1


    INSERT INTO c (c, m)
    SELECT c.id, m.id
    FROM c
    JOIN m ON m.type = 1
    WHERE c.type = 1


    INSERT INTO c (c, m)
    SELECT c.id, m.id
    FROM c
    JOIN m ON c.type = 1
    WHERE m.type = 1


    INSERT INTO c (c, m)
    SELECT c.id, m.id
    FROM c
    JOIN m ON m.type = 1
          AND c.type = 1


    INSERT INTO c (c, m)
    SELECT c.id, m.id
    FROM c
    JOIN m /* ON 1 = 1 */
    WHERE c.type = 1
      AND m.type = 1