select '人数' as type,col_name as value from table1
union all
select '比例' as type,col_name as value from table2
union all
select '均龄' as type,col_name as value from table3
union all
select '比例' as type,col_name as value from table2
union all
select '均龄' as type,col_name as value from table3
select '人数' as type,人数 as value from table1
union all
select '比例' as type,比例 as value from table2
union all
select '均龄' as type,均龄 as value from table3