oracle数据库对test_table表的三个列count1，count2，count3求sum的两种sql，做个记录

• 第一种

select sum (case when count1 is not null then count1 when count2 is not null then count2 when count3 is not null then count3 else '0' end ) a from test_table

• 第二种

select sum(decode(count1,null,0,count1) +decode(count2,count2) +decode(count3,count3)) a from test_table