I am confused about this both from front end point of view as well as querying the data from SQLite Database. If you have any idea how to solve either of these please do answer.
SQLite Database
I have a table likes this:
transactionId | productId | quantity
1 2 1
2 4 0
3 1 null
4 3 1
5 9 1
6 6 0
7 1 1
8 7 1
9 8 1
10 2 1
11 0 null
12 3 1
13 5 1
14 7 1
15 1 0
16 2 1
17 9 1
18 0 null
19 2 1
Now I want to display this data in groups of 5 units(i.e. groups till 5 units are completed) in list in my flutter app.
So 1st group will have 8 items,
2nd will have 6 items,
and 3rd group will have 5 items
(and is still incomplete since more items can be added till quantity for that group becomes 5)
Something like this:
Now my App can have multiple groups like this. Also, I don't think Grid view builder can work here since for each group I'll have to display some data for the group as well as accumulated data (which isn't shown in the picture)
Questions:
1) How to query data from SQFLite database?
2) How to display the queried data in my Flutter App front end?
Unfortunately, this type of problem requires a recursive CTE (or other iterative processing).
Assuming that transactionId is consecutive with no gaps:
with recursive cte as (
select transactionId, productId,
coalesce(quantity, 0) as quantity,
1 as bin
from t
where transactionId = 1
union all
select t.transactionId, t.productId,
(case when cte.quantity > 5
then 0 else cte.quantity
end) + coalesce(t.quantity, 0) as quantity,
(case when cte.quantity > 5 then 1 else 0 end) + cte.bin as bin
from cte join
t
on t.transactionId = cte.transactionId + 1
)
select *
from cte;
If transactionId has gaps or other issues, just use row_number() (in another CTE) to create an appropriate column for the where clauses.
Related
i have a tricky task,
lets assume we have table "Racings", and there we have columns TRACK, CAR, CIRCLE_TIME
here is an example how data could be look like:
id
track
car
circle_time
10
1
10
15
9
1
10
14
8
1
10
16
7
1
10
15
6
1
10
13
5
2
10
7
4
2
10
4
3
2
10
5
2
3
10
8
1
3
10
10
what i need, i to add one more coumn like avg3_circle_time which will show me an average time from last 3 circle_time from each track, example:
id
track
car
circle_time
avg3_circle_time
10
1
10
15
15
9
1
10
14
15
8
1
10
16
14.6
7
1
10
15
null
6
1
10
13
null
5
2
10
7
5.3
4
2
10
4
null
3
2
10
5
null
2
3
10
8
null
1
3
10
10
null
I know how it could works in oracle, you could use something like rowid, but in case of postgresql i don't know, i have a draft like .....avg(circle_time) OVER(PARTITION BY track,car.....) as avg3_circle_time..... help me to solve that task please
You can use window functions to calculate moving averages:
SELECT track, id, car, circle_time, AVG(circle_time) OVER (
PARTITION BY track
ORDER BY id
ROWS BETWEEN 2 PRECEDING AND CURRENT ROW
)
FROM t
ORDER BY track, id
Depending on your definition of previous three, the window could be ROWS BETWEEN 3 PRECEDING AND 1 PRECEDING.
If you want only values when at least 3 circles available
select *
, case when lag(id, 2) over(partition by TRACK, CAR order by id) is not null then
avg(CIRCLE_TIME) over(partition by TRACK, CAR order by id rows between 2 preceding and current row) end a
from Racing
order by id desc;
db<>fiddle
Output
id track car circle_time a
10 1 10 15 15.0000000000000000
9 1 10 14 15.0000000000000000
8 1 10 16 14.6666666666666667
7 1 10 15 null
6 1 10 13 null
5 2 10 7 5.3333333333333333
4 2 10 4 null
3 2 10 5 null
2 3 10 8 null
1 3 10 10 null
Use LAED() then checking one of the next 2 rows is NULL or not. THEN sum of three values for calculating average.
-- PostgreSQL
SELECT *
, CASE WHEN next_circle_time IS NULL OR next_next_circle_time IS NULL
THEN NULL
ELSE ((t.circle_time + COALESCE(next_circle_time, 0) + COALESCE(next_next_circle_time, 0)) / 3 :: DECIMAL) :: DECIMAL(10, 1)
END avg_circle_time
FROM (SELECT *
, LEAD(circle_time, 1) OVER (PARTITION BY track ORDER BY id DESC) next_circle_time
, LEAD(circle_time, 2) OVER (PARTITION BY track ORDER BY id DESC) next_next_circle_time
FROM Racings) t
Another way Use AVG()
SELECT *
, CASE WHEN LEAD(circle_time, 2) OVER (PARTITION BY track ORDER BY id DESC) IS NULL
OR LEAD(circle_time, 1) OVER (PARTITION BY track ORDER BY id DESC) IS NULL
THEN NULL
ELSE AVG(circle_time) OVER (PARTITION BY track ORDER BY id DESC ROWS BETWEEN CURRENT ROW AND 2 FOLLOWING)
END :: DECIMAL(10, 2) avg_circle_time
FROM Racings
Please check from url where both query exists https://dbfiddle.uk/?rdbms=postgres_11&fiddle=f0cd868623725a1b92bf988cfb2deba3
Several of the posted answers end up repeating the window definition. You can avoid this with the window clause:
select *,
case when row_number() over(track_window) > 2
then trunc(avg(CIRCLE_TIME) over(track_window rows 2 preceding), 1)
end a
from Racing
window track_window as (partition by track order by id)
order by id desc
Note how, in this sample, track_window is defined once, then reused for both row_number and avg. In the latter case, the window clause is embellished with a frame as well (rows 2 preceding).
I want to group records by row numbers.
Like from row 1-3 in group 1 , 4-6 in group 2 , 7-9 in group 3 and so on.
Suppose below is the table structure:
Row NumberDataValue
1 A 10
2 A 5
3 A 1
4 A 33
5 A 2
6 A 127
1 B 1
2 B 0
3 B 7
4 B 7
5 B 5
6 B 8
7 B 1
8 B 0
I want a output like this:
GroupValue
1 10
1 5
1 1
2 33
2 2
2 127
1 1
1 0
1 7
2 7
2 5
2 8
3 1
3 0
I am using Oracle 11G.
I can achieve this using PL/SQL. But I have to use SQL only. As I have to use this query in a reporting tool.
If this is a duplicate question please provide the link of the answered question.
Subtract 1 from the column "RowNumber" and divide by 3.
Then use TRUNC() to get the integer part:
SELECT TRUNC(("RowNumber" - 1) / 3) + 1 "Group",
"Value"
FROM tablename
See the demo.
I would assume the name of the first column is ordering.
You can do:
select
1 + trunc(row_number() over(partition by data order by ordering) - 1) / 3,
value
from t
What you show looks like the output from something like this:
select ceil(rn/3) as grp, value
from your_table
order by rn;
Note that "row number" and "group" are reserved words/phrases which should not be used as column names. I used rn and grp instead.
I think the ceiling function is the simplest way to arrive at what you want. If you want to base it on the RowNumber column:
select ceil( RowNumber / 3.0) as grouping
If you want to calculate it yourself using row_number():
select ceil( row_number() over (order by RowNumber) / 3.0 ) as grouping
I have data that looks like this:
ID num_of_days
1 0
2 0
2 8
2 9
2 10
2 15
3 10
3 20
I want to add another column that increments in value only if the num_of_days column is divisible by 5 or the ID number increases so my end result would look like this:
ID num_of_days row_num
1 0 1
2 0 2
2 8 2
2 9 2
2 10 3
2 15 4
3 10 5
3 20 6
Any suggestions?
Edit #1:
num_of_days represents the number of days since the customer last saw a doctor between 1 visit and the next.
A customer can see a doctor 1 time or they can see a doctor multiple times.
If it's the first time visiting, the num_of_days = 0.
SQL tables represent unordered sets. Based on your question, I'll assume that the combination of id/num_of_days provides the ordering.
You can use a cumulative sum . . . with lag():
select t.*,
sum(case when prev_id = id and num_of_days % 5 <> 0
then 0 else 1
end) over (order by id, num_of_days)
from (select t.*,
lag(id) over (order by id, num_of_days) as prev_id
from t
) t;
Here is a db<>fiddle.
If you have a different ordering column, then just use that in the order by clauses.
I have the following table structure.
ITEM TOTAL
----------- -----------------
ID | TITLE ID |ITEMID|VALUE
1 A 1 2 6
2 B 2 1 4
3 C 3 3 3
4 D 4 3 8
5 E 5 1 2
6 F 6 5 4
7 4 5
8 2 8
9 2 7
10 1 3
11 2 2
12 3 6
I am using Apache Derby DB. I need to perform the average calculation in SQL. I need to show the list of item IDs and their average total of the last 3 records.
That is, for ITEM.ID 1, I will go to TOTAL table and select the last 3 records of the rows which are associated with the ITEMID 1. And take average of them. In Derby database, I am able to do this for a given item ID but I cannot make it without giving a specific ID. Let me show you what I've done it.
SELECT ITEM.ID, AVG(VALUE) FROM ITEM, TOTAL WHERE TOTAL.ITEMID = ITEM.ID GROUP BY ITEM.ID
This SQL gives the average of all items in a list. But this calculates for all values of the total tables. I need last 3 records only. So I changed the SQL to this:
SELECT AVG(VALUE) FROM (SELECT ROW_NUMBER() OVER() AS ROWNUM, TOTAL.* FROM TOTAL WHERE ITEMID = 1) AS TR WHERE ROWNUM > (SELECT COUNT(ID) FROM TOTAL WHERE ITEMID = 1) - 3
This works if I supply the item ID 1 or 2 etc. But I cannot do this for all items without giving an item ID.
I tried to do the same thing in ORACLE using partition and it worked. But derby does not support partitioning. There is WINDOW but I could not make use of it.
Oracle one
SELECT ITEMID, AVG(VALUE) FROM(SELECT ITEMID, VALUE, COUNT(*) OVER (PARTITION BY ITEMID) QTY, ROW_NUMBER() OVER (PARTITION BY ITEMID ORDER BY ID) IDX FROM TOTAL ORDER BY ITEMID, ID) WHERE IDX > QTY -3 GROUP BY ITEMID ORDER BY ITEMID
I need to use derby DB for its portability.
The desired output is this
RESULT
-----------------
ITEMID | AVERAGE
1 (9/3)
2 (17/3)
3 (17/3)
4 (5/1)
5 (4/1)
6 NULL
As you have noticed, Derby's support for the SQL 2003 "OLAP Operations" support is incomplete.
There was some initial work (see https://wiki.apache.org/db-derby/OLAPOperations), but that work was only partially completed.
I don't believe anyone is currently working on adding more functionality to Derby in this area.
So yes, Derby has a row_number function, but no, Derby does not (currently) have partition by.
I currently have a table in SQL that looks like this
PRODUCT_ID_1 PRODUCT_ID_2 SCORE
1 2 10
1 3 100
1 10 3000
2 10 10
3 35 100
3 2 1001
That is, PRODUCT_ID_1,PRODUCT_ID_2 is a primary key for this table.
What I would like to do is use this table to add in a row to tell whether or not the current row is the one that maximizes SCORE for a value of PRODUCT_ID_1.
In other words, what I would like to get is the following table:
PRODUCT_ID_1 PRODUCT_ID_2 SCORE IS_MAX_SCORE_FOR_ID_1
1 2 10 0
1 3 100 0
1 10 3000 1
2 10 10 1
3 35 100 0
3 2 1001 1
I am wondering how I can compute the IS_MAX_SCORE_FOR_ID_1 column and insert it into the table without having to create a new table.
You can try like this...
Select PRODUCT_ID_1, PRODUCT_ID_2 ,SCORE,
(Case when b.Score=
(Select Max(a.Score) from TableName a where a.PRODUCT_ID_1=b. PRODUCT_ID_1)
then 1 else 0 End) as IS_MAX_SCORE_FOR_ID_1
from TableName b
You can use a window function for this:
select product_id_1,
product_id_2,
score,
case
when score = max(score) over (partition by product_id_1) then 1
else 0
end as is_max_score_for_id_1
from the_table
order by product_id_1;
(The above is ANSI SQL and should run on any modern DBMS)