MySQL在一張表中的一對多如何查詢

SELECT
	tel,
	GROUP_CONCAT( workno SEPARATOR ',' ) AS workno 
FROM
	test 
GROUP BY
	tel;

去除重複的workno

SELECT
	tel,
	GROUP_CONCAT(DISTINCT workno SEPARATOR ',' ) AS workno 
FROM
	test 
GROUP BY
	tel;