mysql中列转行

在mysql中创建一张表，名为syj；
select * from syj；数据如下：

要实现如下的效果：

代码如下：

select 
sum(case when rowNo%3=1 then id end) no1,
sum(case when rowNo%3=2 then id end) no2,
sum(case when rowNo%3=0 then id end) no3
from (
    select id1 as id,'t1' as t1,(@rowNo:=@rowNo+1) as rowNo from syj,(select @rowNo:=0) rw where  id1!=0 
     union
    select id2 as id,'t2' as t1,(@rowNo:=@rowNo+1) as rowNo from syj,(select @rowNo:=0) rw where  id2!=0 
     union
    select id3 as id,'t3' as t1,(@rowNo:=@rowNo+1) as rowNo from syj,(select @rowNo:=0) rw where  id3!=0 
)edc
GROUP BY t1

继续优化中。。。