技術標籤：mysqli

SELECT
	count( 1 ) 
FROM
	tb_contagion_record a,
	( SELECT student_id, id FROM tb_contagion_record GROUP BY student_id, contagion_event_id ) b 
WHERE
	a.is_delete = 0 
	AND a.id = b.id 
	AND a.org_id = 224285397914628097 
GROUP BY
	prefx

SELECT
	prefx,
	count( DISTINCT student_id, contagion_event_id )
 
 
FROM
	tb_contagion_record 
WHERE
	is_delete = 0 
	AND org_id = 224285397914628097 
GROUP BY
	prefx