I have a user (X) who has been sent 15 emails. There is a field called Opened which is 1 or 0 depending if he opened the emails. I want to work down the list (ordered by date) and start a count each time I get to zero i.e. count each time he gets an email until he opens it. Then I want to average out all the counts. I have tried partitioning and various things but nothing works.
Sorry if I am putting this in the wrong place. This is my final code, should anyone want to do something similar.
Declare #UserCount as Int
Declare #counter as int
Declare #StartEnd as varchar(10)
SET #counter=1
SET #UserCount=1
--Step through the table by user
WHILE #UserCount < (SELECT COUNT(UserID) FROM #Stage2)
BEGIN
--UserProcessOrder is the row number - update the dummy parameter #StartEnd
SET #StartEnd = (SELECT TOP(1) StartEnd FROM #Stage2 WHERE UserProcessOrder=#UserCount)
--Update the table with the counter value
UPDATE #Stage2 SET MaxBeforeOpen=#counter where UserProcessOrder=#UserCount
--Add 1 to the counter so that every time we see START we add 1
SET #Counter = #counter+1
--If we are at the end of the group then re-set the counter
IF #StartEnd='END' SET #counter = 1
--Go to next record for that user
SET #UserCount=#UserCount+1
END
--select * from #Stage2
SELECT AVG(MaxBeforeOpen) as AverageEmailsBeforeOpen
FROM
(
SELECT *
from #Stage2
WHERE StartEnd='END'
) as x
Related
My excel sheet having a column Count is responsible for counting how many times one registration number is repeated as you can see in the given picture.
Whenever I am going to add any new record in my excel table this column go up and count how many records are there as like my reg_no
Let us take Example:
If we add new record at 17th id with
Reg_no = 3591
Name = 'dani'
grade = 'A'
Count ?
Now it will be like Count = 4
I want to convert this table into a SQL query and I am having a problem converting this Count column that how I am going to calculate this count column in SQL
Does anyone know? please help
step 1 create a temp table with empty column
SELECT * , null as desired_column ,
into #yourTable_t1
FROM #yourTable j;
step 2 create a cursor to calculate your desired_column and update temp_table
begin
declare #row int, #order int, #prod varchar(100), #prod_count int =0 ;
declare prod_cur cursor for
SELECT row_num, MyColumn1,MyColumn2
FROM #yourTable_t1 ;
open prod_cur;
fetch next from prod_cur into #row , #order, #prod;
while (##FETCH_STATUS=0)
begin
set #prod_count= ( select count(MyColumn2) from #yourTable_t1 where
MyColumn2= #prod and ROW_NUM <= #row);
update #yourTable_t1
set desired_column = #prod_count
where ROW_NUM= #row;
fetch next from prod_cur into #row , #order, #prod;
end;
close prod_cur;
deallocate prod_cur;
--select * from #yourTable_t1 order by MyColumn2;
end;
Good Luck!
This can be done using window functions
count(*) over (partition by rege_no order by id) as count
Online example
I have a table where item balances are stored.
CREATE TABLE itembalance (
ItemID VARCHAR(15),
RemainingQty INT,
Cost Money,
Id INT
)
I need to make sure that whenever an item is being sent out, the proper balances are deducted from the itembalance table. I do it this way:
DECLARE crsr CURSOR LOCAL FAST_FORWARD FOR
SELECT
itembalance.Cost,
itembalance.RemainingQty
itembalance.Id
FROM dbo.itembalance
WHERE itembalance.ItemID = #v_item_to_be_updated AND RemainingQty > 0
OPEN crsr
FETCH crsr
INTO
#cost,
#qty,
#id
WHILE ##FETCH_STATUS = 0
BEGIN
IF #qty >= #qty_to_be_deducted
BEGIN
UPDATE itembalance SET RemainingQty = RemainingQty - #qty_to_be_deducted WHERE Id = #id
/*do something with cost*/ BREAK
END
ELSE
BEGIN
UPDATE itembalance SET RemainingQty = 0 WHERE Id = #id
/*do something with cost*/ SET #qty_to_be_deducted = #qty_to_be_deducted - #qty
END
FETCH crsr
INTO
#cost,
#qty,
#id
END
CLOSE crsr
DEALLOCATE crsr
The table may contain same item code but with different cost. This code is okay for few items being updated at a time but whenever a lot of items/quantities are being sent out, the process becomes really slow. Is there a way to optimize this code? I am guessing the cursor is making it slow so I want to explore a different code for this process.
This looks like you just need a simple CASE expression:
UPDATE dbo.itembalance
SET Qty = CASE WHEN Qty >= #qty_to_be_deducted THEN Qty - #qty_to_be_deducted ELSE 0 END
WHERE ItemID = #v_item_to_be_updated
--What is the difference between Qty and RemainingQty?
--Why are you checking one and updating the other?
AND RemainingQty > 0;
You code is not very clear as to how and why the mechanism is required and works.
However assuming that you must have multiple records with an outstanding balance, and that you must consider multiple records sequentially as part of this mechanism, then you have two options to solve that within SQL (handling in client code is another option):
1) Use a cursor as you have done
2) Use a temp table or table variable and iterate over it - pretty similar to a cursor but might be faster - you'd have to try and see e.g.
declare #TableVariable table (Cost money, RemainingQty int, Id int, OrderBy int, Done bit default(0))
declare #Id int, #Cost money, #RemainingQty int
insert into #TableVariable (Cost, RemainingQty, Id, OrderBy)
SELECT
itembalance.Cost
, itembalance.RemainingQty
, itembalance.Id
, 1 /* Some order by condition */
FROM dbo.itembalance
WHERE itembalance.ItemID = #v_item_to_be_updated AND RemainingQty > 0
while exists (select 1 from #TableVariable where Done = 0) begin
select top 1 #Id = id, #Cost = Cost, #RemainingQty
from #TableVariable
where Done = 0
order by OrderBy
-- Do stuff here
update #TableVariable set Done = 1 where id = #Id
end
However the code you have shown doesn't appear that it should be slow - so it may be that you are lacking the appropriate indexes, and that a single ItemId update is locking too many rows in the ItemBalance table which is then affecting other ItemId updates.
Could someone please advise on how to repeat the query if it returned no results. I am trying to generate a random person out of the DB using RAND, but only if that number was not used previously (that info is stored in the column "allready_drawn").
At this point when the query comes over the number that was drawn before, because of the second condition "is null" it does not display a result.
I would need for query to re-run once again until it comes up with a number.
DECLARE #min INTEGER;
DECLARE #max INTEGER;
set #min = (select top 1 id from [dbo].[persons] where sector = 8 order by id ASC);
set #max = (select top 1 id from [dbo].[persons] where sector = 8 order by id DESC);
select
ordial,
name_surname
from [dbo].[persons]
where id = ROUND(((#max - #min) * RAND() + #min), 0) and allready_drawn is NULL
The results (two possible outcomes):
Any suggestion is appreciated and I would like to thank everyone in advance.
Just try this to remove the "id" filter so you only have to run it once
select TOP 1
ordial,
name_surname
from [dbo].[persons]
where allready_drawn is NULL
ORDER BY NEWID()
#gbn that's a correct solution, but it's possible it's too expensive. For very large tables with dense keys, randomly picking a key value between the min and max and re-picking until you find a match is also fair, and cheaper than sorting the whole table.
Also there's a bug in the original post, as the min and max rows will be selected only half as often as the others, as each maps to a smaller interval. To fix generate a random number from #min to #max + 1, and truncate, rather than round. That way you map the interval [N,N+1) to N, ensuring a fair chance for each N.
For this selection method, here's how to repeat until you find a match.
--drop table persons
go
create table persons(id int, ordial int, name_surname varchar(2000), sector int, allready_drawn bit)
insert into persons(id,ordial,name_surname,sector, allready_drawn)
values (1,1,'foo',8,null),(2,2,'foo2',8,null),(100,100,'foo100',8,null)
go
declare #min int = (select top 1 id from [dbo].[persons] where sector = 8 order by id ASC);
declare #max int = 1+ (select top 1 id from [dbo].[persons] where sector = 8 order by id DESC);
set nocount on
declare #results table(ordial int, name_surname varchar(2000))
declare #i int = 0
declare #selected bit = 0
while #selected = 0
begin
set #i += 1
insert into #results(ordial,name_surname)
select
ordial,
name_surname
from [dbo].[persons]
where id = ROUND(((#max - #min) * RAND() + #min), 0, 1) and allready_drawn is NULL
if ##ROWCOUNT > 0
begin
select *, #i tries from #results
set #selected = 1
end
end
I have a While loop where I am trying to insert.
DECLARE #CurrentOffer int =121
DECLARE #OldestOffer int = 115
DECLARE #MinClubcardID bigint=0
DECLARE #MaxClubcardID bigint=1000
WHILE 1 = 1
BEGIN
INSERT INTO Temp WITH (TABLOCK)
SELECT top (100) clubcard from TempClub with (nolock) where ID between
#MinClubcardand and #MaxClubcard
declare #sql varchar (8000)
while #OldestOffer <= #CurrentOffer
begin
print #CurrentOffer
print #OldestOffer
set #sql = 'delete from Temp where Clubcard
in (select Clubcard from ClubTransaction_'+convert(varchar,#CurrentOffer)+' with (nolock))'
print (#sql)
exec (#sql)
SET #CurrentOffer = #CurrentOffer-1
IF #OldestOffer = #CurrentOffer
begin
-- my logic
end
end
end
My TempClub table always checks only with first 100 records. My TempClub table has 3000 records.
I need to check all my clubcard all 3000 records with ClubTransaction_121,ClubTransaction_120,ClubTransaction_119 table.
The SELECT query in line 8 returns only the top 100 items
SELECT top (100) clubcard from TempClub ...
If you want to retrieve all items, remove the top (100) part of your statement
SELECT clubcard from TempClub ...
In order to do batch type processing, you need to set the #MinClubcardID to the last ID processed plus 1 and include an ORDER BY ID to ensure that the records are being returned in order.
But... I wouldn't use the approach of using the primary key as my "index". What you're looking for is a basic pagination pattern. In SQL Server 2005+, Microsoft introduced the row_number() function which makes pagination a lot easier.
For example:
DECLARE #T TABLE (clubcard INT)
DECLARE #start INT
SET #start = 0
WHILE(1=1)
BEGIN
INSERT #T (clubcard)
SELECT TOP 100 clubcard FROM
(
SELECT clubcard,
ROW_NUMBER() OVER (ORDER BY ID) AS num
FROM dbo.TempClub
) AS t
WHERE num > #start
IF(##ROWCOUNT = 0) BREAK;
-- update counter
SET #start = #start + 100
-- process records found
-- make sure temp table is empty
DELETE FROM #T
END
Say i'm dealing with 10 library cards, each card has customer values (eg. member number, member name ...) and I need to update a value for each card.
If i want to grab all ten from the database but only want to update each row one at a time, is there an alternative to a cursor? I know a while loop might work but how would I be able to grab one row every time it loops until I am done with all 10 cards?
Don't need to use cursors. I use this most of the time:
declare #uid int -- this is the type unique index on the table you're updating
-- Copy out the unique ids of the rows you want to update to a temporary table
select uid into #temp from customers -- you can use a where condition here
-- Loop through the rows of the temp table
while exists (select 1 from #temp)
begin
set rowcount 1
select #uid = uid from #temp -- pull one uid from the temp table
set rowcount 0
delete from #temp where uid = #uid -- delete that uid from the temp table
-- Do something with the uid you have
update customers set name = 'Joe Shmoe' where uid = #uid
end
It is possible to loop on the table using a clustered index on a particular column. Because the clustered index arranges the rows in sorted order, it can be used like an index variable of loop.
declare #uid int
select #uid = 0 -- assume the uids in table are > 0
declare #rowsaf int
select #rowsaf = 1
while #rowsaf > 1
begin
set rowcount 1
select #uid = uid from customers where uid > #uid
select #rowsaf = ##rowcount
-- update the row using #uid
end
set rowcount 0
Here is the article that explains it in detail.