Creating alternating 0 and 1 values based on changing data value - sql

Question

I have data in my sql database and need to create changeControl value.
data changeControl
M-0101 0
M-0101 0
M-02 1
M-03 0
OT-014 1
OT-014 1
M-228 0
M-228 0
Are there any way to create this changeControl value depend on data?

Answer 1

There is an easy way, but it depend on your DB.
In SQL Server and in Oracle you can use DENSE_RANK() to get the order of the values, using that you'll have the same number for equal values
In SQL Server
SELECT data
, (DENSE_RANK() OVER (ORDER BY data) - 1) % 2 changeControl
FROM Table1
In Oracle the % is not present, we need to use the function MOD()
SELECT data
, MOD((DENSE_RANK() OVER (ORDER BY data) - 1), 2) changeControl
FROM Table1
In MySQL there is no DENSE_RANK, but there is another way to get the result
SELECT data, changeControl
FROM (SELECT #last
, data
, #id := CASE WHEN #last <> data THEN 1 - #id
WHEN #last = data THEN #id
ELSE 0
END changeControl
, #last:= data
FROM Table1
, (SELECT #id := 0) a) b
if you don't mind additional column you can run directly the subquery.
p.s.: If you don't specify what DB you're using we have to guess.

Answer 2

You need to first break your data into groups, and assign each group a number.
Then join this information with main table, sort by data, and take modulo by two from group number - this will be your changeControl column.
select tn.*, t.RN % 2 as changeControl from tableName tn
left join
(select ROW_NUMBER() OVER (ORDER BY data) AS RN, data
from tableName group by data) t
on t.data = tn.data
order by tn.data
This problem cannot be solved by taking modulo by two of id or data hash - id keeps changing even for identical values, and two sequential hashes although may be different, can both be even, producing same 'changeControl' value.

Answer 3

To implement this, you should handle the RowStyle event of the GridView. Here is some sample code:
using DevExpress.XtraGrid.Views.Grid;
private void gridView1_RowStyle(object sender,
DevExpress.XtraGrid.Views.Grid.RowStyleEventArgs e) {
GridView View = sender as GridView;
if(e.RowHandle >= 0) {
int changeControl = Convert.ToInt32(View.GetRowCellValue(e.RowHandle, View.Columns["changeControl"]));
if(changeControl == 1) {
e.Appearance.BackColor = Color.Salmon;
}
else
e.Appearance.BackColor = Color.SeaShell;
}
}
Please also review this example:
How to change a row style based on a column value

Answer 4

You can create alternatining 0 and 1 values for change control column based on where id is odd or even
SELECT id , data ,
CASE WHEN id%2=0 THEN 1 ELSE 0 END as changecontrol
FROM tableName
EDIT
SELECT id , data ,
CASE WHEN
RIGHT(data,LEN(data) - CHARINDEX('-',data)) % 2 = 0
THEN 1
ELSE 0 END as changecontrol
FROM tableName