I want to display some data and my requirement is repeated values should not be shown adjacent.
Right now the data in the table is in this order
ID Name
1 A
2 A
3 B
4 C
5 B
6 B
7 C
8 C
9 C
Expected result - It should be in below order
ID Name
1 A
3 B
4 C
2 A
5 B
7 C
6 B
8 C
9 C
This can be done using the ROW_NUMBER window function.
SELECT *, ROW_NUMBER() OVER (PARTITION BY Name ORDER BY ID) AS rn
FROM mytable
ORDER BY rn, Name
db<>fiddle
You can put row_number() directly in the order by. I would recommend:
select t.*
from t
order by row_number() over (partition by name order by id),
name;
Related
I've got a column with non-unique values like so:
ID COL_A
0 A
1 B
2 B
3 C
4 D
5 D
6 D
7 E
I would like to select an offset in addition to those two columns which produces the following output:
ID COL_A OFFSET
0 A 0
1 B 0
2 B 1
3 C 0
4 D 0
5 D 1
6 D 2
7 E 0
The offset should be applied so that the value with the lower primary key receives the lower offset.
I could probably come up with a PL/SQL approach to get this, but is this possible in pure SQL?
The row_number() window function is just what the doctor prescribed:
SELECT id, col_a, ROW_NUMBER() OVER (PARTITION BY col_a ORDER BY id) - 1 AS offset
FROM mytable
USE ROW_NUMBER
SELECT COL1,COL2,ROW_NUMBER() OVER (PARTITION BY COL2 ORDER BY Col1) Seq
FROM TableNAme
Consider Table like this.
I will call it Test
Id A B C D
1 1 1 8 25
2 1 2 5 35
3 1 3 2 75
4 2 2 2 45
5 3 2 5 26
Now I want rows with max 'Id' Grouped by 'A'
Id A B C D
3 1 3 2 75
4 2 2 2 45
5 3 2 5 26
-
--Work, but I do not want
SELECT MAX(Id), A FROM Test GROUP BY A
--I want but do not work
SELECT MAX(Id), A, B, C, D FROM Test GROUP BY A
--Work but I do not want
SELECT MAX(Id), A, B, C, D FROM Test GROUP BY A, B, C, D
--Work and I want
SELECT old.Id, old.A, new.B, new.C, new.D
FROM(
SELECT
MAX(Id) AS Id, A
FROM
Test GROUP BY A
)old
JOIN Test new
ON old.Id = new.Id
Is there a better way to write last query without join
Most databases support window functions:
select *
from (
select *, row_number() over (partition by a order by id desc) rn
from test
) t
where rn = 1
Most DBMS now support Common Table Expressions (CTE). You can use one.
;with maxa as (
select row_number() over(partition by a order by id desc) rn,
id,a,b,c,d from test
)
select id,a,b,c,d
from maxa
where rn=1
I have the following table:
Name Field
A 1
B 1
C 1
D 1
E 1
F 1
G 1
H 2
I 2
J 2
K 3
L 3
M 3
N 3
O 3
P 3
Q 3
R 3
S 3
T 3
I need a SQL query which will generate me a set with 5 random rows for each distinct value on column Field.
For example, results expected:
Name Field
A 1
B 1
D 1
E 1
G 1
J 2
I 2
H 2
M 3
Q 3
T 3
S 3
P 3
Is there an easy way to do this? Or should i split that table into more tables and generate random for each table then union them?
You can do this with a CTE using a ROW_NUMBER() whilst PARTITIONing on the Field:
;With Cte As
(
Select Name, Field,
Row_Number() Over (Partition By Field Order By NewId()) RN
From YourTable
)
Select Name, Field
From Cte
Where RN <= 5
SQL Fiddle
You can readily do this with row_number():
select name, field
from (select t.*,
row_number() over (partition by field order by newid()) as seqnum
from t
) t
where seqnum <= 5;
An enhancement to Gordon Linoff's code, This code really helped me if you need criteria in your query.
select *
from (select t.*,
row_number() over (partition by region order by newid()) as seqnum
from MyTable t
WHERE t.program = 'ACME'
) t
where seqnum <= 1500;
I'm trying to achieve the following "rank" result given the original dataset composed by the column ID and CODE.
id code rank
1 A 1
2 A 1
3 A 1
4 B 2
5 B 2
6 C 3
7 C 3
8 C 3
9 A 4
10 A 4
Using the RANK_DENSE instruction over the CODE column i get the following result (with the A code getting the same rank value also after "the break" between the rows)
id code rank
1 A 1
2 A 1
3 A 1
4 B 2
5 B 2
6 C 3
7 C 3
8 C 3
9 A 1
10 A 1
Is it possible to achieve the results as shown in the first (example) table, with the A code changing rank when there is a separation between the group formed by id: 1-2-3 and the one formed by id: 9-10 without using a cursor?
Thanks
You want to find sequences of values and give them a rank. You can do this with a difference of row numbers approach. The following assigns a different number to each grouping:
select o.*, dense_rank() over (order by grp, code)
from (select o.*,
(row_number() over (order by id) -
row_number() over (partition by code order by id)
) as grp
from original o
) o;
If you want the assignment in the same order as the original data, then you can order by the id, but that requires an additional window function:
select o.*, dense_rank() over (order by minid) as therank
from (select o.*, min(id) over (partition by grp, code) as minid
from (select o.*,
(row_number() over (order by id) -
row_number() over (partition by code order by id)
) as grp
from original o
) o
) o;
SUM by if current is the same as previous row. Works from SQL Server 2012.
WITH CTE AS (
SELECT id, code,
CASE Code WHEN LAG(CODE) OVER (ORDER BY id) THEN 0 ELSE 1 END AS Diff
FROM Table1)
SELECT id, code, SUM(Diff) OVER (ORDER BY id) FROM CTE
Please also see similar question at How to make row numbering with ordering, partitioning and grouping
I have a table which has 3 columns A, B, C
I want to do a query like this:
select A, Max(B), ( C in the row having max B ) from Table group by A.
is there a way to do such a query?
Test Data:
A B C
2 5 3
2 6 1
4 5 1
4 7 9
6 5 0
the expected result would be:
2 6 1
4 7 9
6 5 0
;WITH CTE AS
(
SELECT A,
B,
C,
RN = ROW_NUMBER() OVER(PARTITION BY A ORDER BY B DESC)
FROM YourTable
)
SELECT A, B, C
FROM CTE
WHERE RN = 1
Try this
select t.*
from table t
join (Select A,max(b) B from table group by A) c
on c.a=t.a
and c.b=a.b