Given the Sequence of numbers below, how can I assign a Sequence number so that each block which starts with a 1 and ends with a 0 is given a unique identifying number? How can I create the Sequence Number column using TSQL?
Sequence
SequenceNumber
1
1
1
1
0
1
1
2
1
2
1
2
0
2
1
3
0
3
Use COUNT OVER to count zeros. You need some column to determine the order. I am calling it sortkey in the following query:
select
t.*,
count(case when sequence = 0 then 1 end)
over (order by sortkey
rows between unbounded preceding and 1 preceding) + 1
as sequence_number
from mytable t
order by sortkey;
Demo: https://dbfiddle.uk/3DZBeDMQ
Related
I have data as below where for one customer ID there are several orders (KEY) which is the primary key. I have also have a activity flag as below (either 0 or 1).
CUST_ID KEY FLAG
1 1 1
1 2 1
1 3 1
1 4 0
1 5 0
1 6 1
1 7 1
1 8 0
1 9 0
Now I want to create ranks as below based on the FLAG. The idea is to give same Rank as preceding row if the FLAG is same as preceding row. The Rank increments if the current value is different from preceding value.
CUST_ID KEY FLAG RN
1 1 1 1
1 2 1 1
1 3 1 1
1 4 0 2
1 5 0 2
1 6 1 3
1 7 1 3
1 8 0 4
1 9 0 4
I'm new to SQL, so please let me know if I need to reframe my question.
Use LAG() window function to get each row's previous flag and then use SUM() window function to create the rankings:
SELECT CUST_ID, KEY, FLAG,
SUM(CASE WHEN FLAG <> prev_FLAG THEN 1 END) OVER (PARTITION BY CUST_ID ORDER BY KEY) RN
FROM (
SELECT *, LAG(FLAG, 1, FLAG - 1) OVER (PARTITION BY CUST_ID ORDER BY KEY) prev_FLAG
FROM tablename
) t;
See the demo.
The code could be simplified, depending on the specific database that you use.
I have 2 simple columns:
one column is simply an ID column and the other column is some sort of boolean type column.
ID V
0 1
1 0
2 0
3 1
4 1
5 0
I want to order the rows by pair of values (0,1) of column V
(while still keeping the ID as minimal as possible):
ID V
1 0
0 1
2 0
3 1
5 0
4 1
How do I do that ?
Seems you want get rows for 0 and 1 in turn:
select id, v
from tab
order by
row_number()
over (partition by v
order by id)
,v
Data Looks like -
1
2
3
1
2
2
2
3
1
5
4
1
2
So whenever there is a 1, it marks the beginning of a group which includes all the elements until it hits the next 1. So here,
1 2 3 - group 1
1 2 2 2 3 - group 2
and so on..
What would be the SQL query to show the average for every such group.
I could not figure out how to group them without using for loops or PLSQL code.
Result should look like two columns, one with the actual data and col 2 with the average value-
1 - avg value of 1,2 3
2
3
1 - avg value of 1,2,2,2,3
2
2
2
3
1 - avg value of 1,5,4
5
4
1 - avg value of 1,2
2
SQL tables represent unordered sets. There is no ordering, unless a column specifies the ordering. Let me assume that you have such a column.
You can identify the groups using a cumulative sum:
select t.*,
sum(case when t.col = 1 then 1 else 0 end) over (order by ?) as grp
from t;
? is the column that specifies the ordering.
You can then calculate the average using aggregation:
select grp, avg(col)
from (select t.*,
sum(case when t.col = 1 then 1 else 0 end) over (order by ?) as grp
from t
) t
group by grp;
I have a group of rows in order. Column "Status" has only two value 0/1. Now, I'd like to add a sequence number / group number for each 0/1 set. there can be 1 to many rows of 0's but only one 1 for each set in the end. How do I add a new column as sequence number that only increases when there is a 1.
example:
ID Status Row Group Number
1 0 1
2 0 1
3 1 1
4 0 2
5 1 2
6 0 3
7 0 3
8 0 3
9 1 3
question is how do I get the third column?
thank you.
Hmmm . . . This is a cumulative sum up to the previous row (plus 1). So, in SQL Server 2012+, you can do:
select t.*,
1 + sum(status) over (order by id) - status as rowgroupnumber
from t;
I m working on weird SQL query
Patient_ID Count order_no
1 1 1
2 1 2
2 0 3
2 0 4
3 1 5
3 0 6
where I need to count the patient as above, for every new patient , the count column is 1.
If repeated , the below entry it should be 0
I m confused how should make that work in SQL
In order to make the first entry 1 and all subsuqent entries 0, I believe you need a ranking with partition by the order number. Please checkout the sqlfiddle below to test results.
http://www.sqlfiddle.com/#!3/4e2e2/17/0
SELECT
patient_id
,CASE WHEN r.rank = 1
THEN 1
ELSE 0
END
, order_number
FROM
(
SELECT
order_number
,patient_id
,ROW_NUMBER() OVER (PARTITION BY patient_id ORDER BY order_number)[rank]
FROM
PatientTable
)r