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declare @a char(20)
select * from AAA
union all
if @a=1
begin
select * from BBB
end
Else
begin
select * from CCC
and
union all
select * from DDD
declare @a varchar(100),@sql varchar(1000)
set @sql='select * from AAA'
if @a=1
set @sql=@sql+' union all select * from BBB'
else
set @sql=@sql+' union all select * from CCC '
set @sql=@sql+'union all select * from DDD'
exec (@sql)
declare @a char(20)
select * from AAA
if @a=1
begin
select * from BBB
end
Else
begin
select * from CCC
union all
select * from DDD
end
declare @a char(20)
select * from AAA
union all
select * from BBB where @a=1 --当@a=1时,这个条件成立,ccc后面的不成立
union all
select * from CCC where @a<>1 --当@a不等于1时,这个条件成立,bbb后面的不成立
union all
select * from DDD
declare @a varchar(100),@sql varchar(1000)
set @sql='select * from AAA'
if @a=1
set @sql=' union all select * from BBB'
else
set @sql=' union all select * from CCC union all select * from DDD'
exec (@sql)
declare @a char(20)
select * from AAA
union all
select * from BBB where @a=1
union all
select * from CCC where @a<>1
union all
select * from DDD