TSQL - Referencing a changed value from previous row
I am trying to do a row calculation whereby the larger value will carry forward to the subsequent rows until a larger value is being compared. It is done by comparing the current value to the previous row using the lag() function.
Code
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
SELECT id
,d1
,d2 = CASE WHEN id <> (LAG(id,1,0) OVER (ORDER BY id,d1)) THEN d2
WHEN d2 < (LAG(d2,1,0) OVER (ORDER BY id,d1)) THEN (LAG(d2,1,0) OVER (ORDER BY id,d1))
ELSE d2 END
Output (Added row od2 for clarity)
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 4 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 3 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
As you can see from the output it lag function is referencing the original value of the previous row rather than the new value. Is there anyway to achieve this?
Desired Output
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 5 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 4 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
sql sql-server tsql sql-server-2012
add a comment |
I am trying to do a row calculation whereby the larger value will carry forward to the subsequent rows until a larger value is being compared. It is done by comparing the current value to the previous row using the lag() function.
Code
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
SELECT id
,d1
,d2 = CASE WHEN id <> (LAG(id,1,0) OVER (ORDER BY id,d1)) THEN d2
WHEN d2 < (LAG(d2,1,0) OVER (ORDER BY id,d1)) THEN (LAG(d2,1,0) OVER (ORDER BY id,d1))
ELSE d2 END
Output (Added row od2 for clarity)
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 4 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 3 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
As you can see from the output it lag function is referencing the original value of the previous row rather than the new value. Is there anyway to achieve this?
Desired Output
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 5 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 4 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
sql sql-server tsql sql-server-2012
add a comment |
I am trying to do a row calculation whereby the larger value will carry forward to the subsequent rows until a larger value is being compared. It is done by comparing the current value to the previous row using the lag() function.
Code
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
SELECT id
,d1
,d2 = CASE WHEN id <> (LAG(id,1,0) OVER (ORDER BY id,d1)) THEN d2
WHEN d2 < (LAG(d2,1,0) OVER (ORDER BY id,d1)) THEN (LAG(d2,1,0) OVER (ORDER BY id,d1))
ELSE d2 END
Output (Added row od2 for clarity)
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 4 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 3 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
As you can see from the output it lag function is referencing the original value of the previous row rather than the new value. Is there anyway to achieve this?
Desired Output
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 5 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 4 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
sql sql-server tsql sql-server-2012
I am trying to do a row calculation whereby the larger value will carry forward to the subsequent rows until a larger value is being compared. It is done by comparing the current value to the previous row using the lag() function.
Code
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
SELECT id
,d1
,d2 = CASE WHEN id <> (LAG(id,1,0) OVER (ORDER BY id,d1)) THEN d2
WHEN d2 < (LAG(d2,1,0) OVER (ORDER BY id,d1)) THEN (LAG(d2,1,0) OVER (ORDER BY id,d1))
ELSE d2 END
Output (Added row od2 for clarity)
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 4 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 3 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
As you can see from the output it lag function is referencing the original value of the previous row rather than the new value. Is there anyway to achieve this?
Desired Output
+----+----+----+ +----+
| id | d1 | d2 | | od2|
+----+----+----+ +----+
| A | 0 | 5 | | 5 |
| A | 1 | 5 | | 2 |
| A | 2 | 5 | | 4 |
| A | 3 | 6 | | 6 |
| B | 0 | 4 | | 4 |
| B | 2 | 4 | | 3 |
| B | 3 | 4 | | 2 |
| B | 4 | 5 | | 5 |
+----+----+----+ +----+
sql sql-server tsql sql-server-2012
sql sql-server tsql sql-server-2012
asked Nov 16 '18 at 7:54
KyriveKyrive
424
424
add a comment |
add a comment |
2 Answers
2
active
oldest
votes
Try this:
SELECT id
,d1
,d2
,MAX(d2) OVER (PARTITION BY ID ORDER BY d1)
FROM @TAB
The idea is to use the MAX
to get the max value from the beginning to the current row for each partition.
add a comment |
Thanks for providing the DDL scripts and the DML.
One way of doing it would be using recursive cte as follows.
1. First rank all the records according to id, d1 and d2. -> cte block
2. Use recursive cte and get the first elements using rnk=1
3. the field "compared_val" will check against the values from the previous rnk to see if the value is > than the existing and if so it would swap
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
;with cte
as (select row_number() over(partition by id order by d1,d2) as rnk
,id,d1,d2
from @TAB
)
,data(rnk,id,d1,d2,compared_val)
as (select rnk,id,d1,d2,d2 as compared_val
from cte
where rnk=1
union all
select a.rnk,a.id,a.d1,a.d2,case when b.compared_val > a.d2 then
b.compared_val
else a.d2
end
from cte a
join data b
on a.id=b.id
and a.rnk=b.rnk+1
)
select * from data order by id,d1,d2
add a comment |
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
Try this:
SELECT id
,d1
,d2
,MAX(d2) OVER (PARTITION BY ID ORDER BY d1)
FROM @TAB
The idea is to use the MAX
to get the max value from the beginning to the current row for each partition.
add a comment |
Try this:
SELECT id
,d1
,d2
,MAX(d2) OVER (PARTITION BY ID ORDER BY d1)
FROM @TAB
The idea is to use the MAX
to get the max value from the beginning to the current row for each partition.
add a comment |
Try this:
SELECT id
,d1
,d2
,MAX(d2) OVER (PARTITION BY ID ORDER BY d1)
FROM @TAB
The idea is to use the MAX
to get the max value from the beginning to the current row for each partition.
Try this:
SELECT id
,d1
,d2
,MAX(d2) OVER (PARTITION BY ID ORDER BY d1)
FROM @TAB
The idea is to use the MAX
to get the max value from the beginning to the current row for each partition.
answered Nov 16 '18 at 7:59
gotqngotqn
20.8k32119194
20.8k32119194
add a comment |
add a comment |
Thanks for providing the DDL scripts and the DML.
One way of doing it would be using recursive cte as follows.
1. First rank all the records according to id, d1 and d2. -> cte block
2. Use recursive cte and get the first elements using rnk=1
3. the field "compared_val" will check against the values from the previous rnk to see if the value is > than the existing and if so it would swap
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
;with cte
as (select row_number() over(partition by id order by d1,d2) as rnk
,id,d1,d2
from @TAB
)
,data(rnk,id,d1,d2,compared_val)
as (select rnk,id,d1,d2,d2 as compared_val
from cte
where rnk=1
union all
select a.rnk,a.id,a.d1,a.d2,case when b.compared_val > a.d2 then
b.compared_val
else a.d2
end
from cte a
join data b
on a.id=b.id
and a.rnk=b.rnk+1
)
select * from data order by id,d1,d2
add a comment |
Thanks for providing the DDL scripts and the DML.
One way of doing it would be using recursive cte as follows.
1. First rank all the records according to id, d1 and d2. -> cte block
2. Use recursive cte and get the first elements using rnk=1
3. the field "compared_val" will check against the values from the previous rnk to see if the value is > than the existing and if so it would swap
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
;with cte
as (select row_number() over(partition by id order by d1,d2) as rnk
,id,d1,d2
from @TAB
)
,data(rnk,id,d1,d2,compared_val)
as (select rnk,id,d1,d2,d2 as compared_val
from cte
where rnk=1
union all
select a.rnk,a.id,a.d1,a.d2,case when b.compared_val > a.d2 then
b.compared_val
else a.d2
end
from cte a
join data b
on a.id=b.id
and a.rnk=b.rnk+1
)
select * from data order by id,d1,d2
add a comment |
Thanks for providing the DDL scripts and the DML.
One way of doing it would be using recursive cte as follows.
1. First rank all the records according to id, d1 and d2. -> cte block
2. Use recursive cte and get the first elements using rnk=1
3. the field "compared_val" will check against the values from the previous rnk to see if the value is > than the existing and if so it would swap
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
;with cte
as (select row_number() over(partition by id order by d1,d2) as rnk
,id,d1,d2
from @TAB
)
,data(rnk,id,d1,d2,compared_val)
as (select rnk,id,d1,d2,d2 as compared_val
from cte
where rnk=1
union all
select a.rnk,a.id,a.d1,a.d2,case when b.compared_val > a.d2 then
b.compared_val
else a.d2
end
from cte a
join data b
on a.id=b.id
and a.rnk=b.rnk+1
)
select * from data order by id,d1,d2
Thanks for providing the DDL scripts and the DML.
One way of doing it would be using recursive cte as follows.
1. First rank all the records according to id, d1 and d2. -> cte block
2. Use recursive cte and get the first elements using rnk=1
3. the field "compared_val" will check against the values from the previous rnk to see if the value is > than the existing and if so it would swap
DECLARE @TAB TABLE (id varchar(1),d1 INT , d2 INT)
INSERT INTO @TAB (id,d1,d2)
VALUES ('A',0,5)
,('A',1,2)
,('A',2,4)
,('A',3,6)
,('B',0,4)
,('B',2,3)
,('B',3,2)
,('B',4,5)
;with cte
as (select row_number() over(partition by id order by d1,d2) as rnk
,id,d1,d2
from @TAB
)
,data(rnk,id,d1,d2,compared_val)
as (select rnk,id,d1,d2,d2 as compared_val
from cte
where rnk=1
union all
select a.rnk,a.id,a.d1,a.d2,case when b.compared_val > a.d2 then
b.compared_val
else a.d2
end
from cte a
join data b
on a.id=b.id
and a.rnk=b.rnk+1
)
select * from data order by id,d1,d2
answered Nov 16 '18 at 8:10
George JosephGeorge Joseph
1,590510
1,590510
add a comment |
add a comment |
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