Mysql中连续行之间的区别

Question

I would like to get the difference between 2 consecutive rows in the MySql. I am trying to resolve, but no luck. Here is the data in the image

I need a difference between rows of "Data2" column and results into "Diff" column.

Thanks for your kind attention and much appreciated for your help.

-Ram

Answer 1

If the table have an auto incremental column 'id', We can order by id and identify the next row value and subtract it

SELECT t1.*, t1.Data2-(SELECT t2.Data2 FROM  `table_name`  t2 WHERE t2.id > t1.id LIMIT 1 ) AS difference
FROM `table_name`  t1
ORDER BY t1.id

to subtract from next row value

SELECT t1.*, t1.Data2-(SELECT t2.Data2 FROM  `table_name`  t2 WHERE t2.id < t1.id ORDER BY id DESC  LIMIT 1 ) AS difference
FROM `table_name`  t1
ORDER BY t1.id

Answer 2

Since you don't have a unique column in your table, you can achieve this by including a bind variable [ @rn & @rn1 ] which adds a unique number sequentially to every row in the table.

Try this:

SELECT tab1.application_id, tab1.fiscal_year, tab1.data1, coalesce(cast(tab1.data2 as signed) - 
                cast(tab2.data2 as signed), tab1.data2) as diff
  FROM 
      (SELECT b.application_id, @rn1:=@rn1+1 AS rank, b.fiscal_year, b.data1, b.data2
         FROM your_table b, (SELECT @rn1:=0) t1) as tab1,
      (SELECT a.application_id, @rn:=@rn+1 AS rank, a.fiscal_year, a.data1, a.data2
         FROM your_table a, (SELECT @rn:=0) t2) as tab2
 WHERE tab1.rank = tab2.rank + 1;