Finds donors who have contributed to multiple 2016 campaigns.

compare_candidates.sql

ALTER TABLE contributions_individual ADD COLUMN contbr_nm_short varchar(200);

UPDATE contributions_individual set contbr_nm_short = SUBSTRING_INDEX(contributions_individual.contbr_nm, ' ', 2);

SELECT contributions_individual.cand_nm, 
	contributions_individual.contbr_nm_short,
	contributions_individual.contbr_zip,
	SUM(contributions_individual.contb_receipt_amt) as total, 
	b.cand_nm, 
	b.contbr_nm_short, 
	b.contbr_zip,
	b.total
FROM contributions_individual
JOIN (
	SELECT cand_nm, 
		contbr_nm_short,
		contbr_zip, 
		SUM(contb_receipt_amt) as total 
	FROM contributions_individual
	GROUP BY cand_nm, contbr_nm, contbr_zip
) as b
ON contributions_individual.contbr_nm_short = b.contbr_nm_short
	AND LEFT(contributions_individual.contbr_zip, 5) = LEFT(b.contbr_zip, 5)
	AND contributions_individual.cand_nm != b.cand_nm
GROUP BY contributions_individual.cand_nm, contributions_individual.contbr_nm, contributions_individual.contbr_zip;

Initalizing.

Added an ALTER TABLE to add a condensed contributor name to the basic file, allowing better joins between candidates (who do annoying stuff to names, like add "Mr." sometimes).