union 按顺序合并结果集

union 按顺序合并结果集

例如:

select  'B701' as intf
union all
select  'B702' as intf 
union all
select  'B703' as intf 
union all
select  'B704' as intf 
union all
select  'B705' as intf 
union all
select  'B706' as intf 
union all
select  'B707' as intf 
union all
select  'B709' as intf 
union all
select  'B301V2' as intf

结果:

现在将B701和B301V2换一个位置

select  'B301V2' as intf
union all
select  'B702' as intf 
union all
select  'B703' as intf 
union all
select  'B704' as intf 
union all
select  'B705' as intf 
union all
select  'B706' as intf 
union all
select  'B707' as intf 
union all
select  'B709' as intf 
union all
select  'B701' as intf

结果:

结论：

union 合并结果集的时候是按照SQL写的位置顺序来进行合并的