将两条sql合并为一个，即为 select .. K19,... L19 这样语句？在线等大牛帮忙

Question

1.select sum(a.aaa) as K19 from a where ((a.bbb = '1')
2.select sum(a.aaa) as L19 from a where ((a.bbb = '2')

Answer 1

select sum(case when a.bbb='1' then a.aaa else 0 end) as K19,sum(case when a.bbb='2' then a.aaa else 0 end) as L19 from a;