想把b表放到sum里面进行查询,只留 a表(from a),这种的,怎么改啊 ?不要left join b这个了SELECT SUM( CASE WHEN(( a.c_ajzlb = 'aaa' OR a.c_ajzlb = 'bbb' OR a.c_ajzlb = 'ccc' )) AND b.d_hxjarq BETWEEN '2020-01-01' AND '2020-06-01' THEN 1 ELSE 0 END ) 数1from aleft JOIN b on a.c_bh = b.c_ajbh