I have a transactions table which has shows various transactions made by several accounts. Some make only one, others more than that. At the moment the SQL I have prints out the first purchase of each account but i need it to print out the second made by each account
SELECT account_id
, purchase_date as second_purchase
, amount as second_purchase_amount
FROM Transactions t
WHERE purchase_date NOT IN (SELECT MIN(purchase_date)
FROM Transactions m
)
GROUP BY account_id
HAVING purchase_date = MIN(purchase_date);
What needs to change that the second purchase date and amount are chosen? I tried adding in a count for the account_id but it was giving me the wrong value.
You can use variables to assign row numbers and get the 2nd purchase.
SELECT account_id,purchase_Date,amount
FROM (
SELECT account_id
,purchase_date
,amount
--, #rn:=IF(account_id=#a_id and #pdate <> purchase_date,#rn+1,1) as rnum
,case when account_id=#a_id and #pdate <> purchase_date then #rn:=#rn+1
when account_id=#a_id and #pdate=purchase_date then #rn:=#rn
else #rn:=1 end as rnum
, #pdate:=purchase_date
, #a_id:=account_id
FROM Transactions t
CROSS JOIN (SELECT #rn:=0,#a_id:=-1,#pdate:='') r
ORDER BY account_id, purchase_date
) x
WHERE rnum=2
Explanation of how it works:
#rn:=0,#a_id:=-1,#pdate:='' - Declare 3 variables and initialize them, #rn for assigning the row numbers, #a_id to hold the account_id and #pdate to hold the purchase_date.
For the first row (ordered by account_id and purchase_date), account_id and #a_id, #pdate and purchase_date will be compared. As they wouldn't be equal, the when conditions fail and the else part would assign #rn=1. Also, the variable assignment happens after this. #aid and #pdate would be updated to current row's values. For the second row, if they are the same account and on a different date the first when condition will be executed and the #rn will be incremented by 1. If there are ties the second when condition would be executed and the #rn remains the same. You can run the inner query to check how the variables are assigned.
Number the rows and choose RowNumber = 2
select *
from (
select
#rn := case when #account_id = account_id then #rn + 1 else #rn := 1 end as RowNumber,
#account_id := account_id as account_id,
purchase_date
from
(select #rn := 1) x,
(select #acount_id :=account_id as account_id, purchase_date
from Transactions
order by account_id, purchase_date) y
) z
where RowNumber = 2;
Related
Get only the biggest date:
These are check-in and check-out records of employees, some times they do twice or more entries on the system in a row. In this sample there were two check-out in a row. Assuming these rows always gonna be ordered, in the case of check-out I would like have the biggest date, and in the case of the check-in the smallest date.
In that case I would like to have this:
The smaller date was excluded:
DEMO
Try this, in this big CASE statement I increment column by one, if checkin switches from null to not null and the other way around. Then it's enough to group by this column taking max and min of checkout and checkin respectively:
select #checkinLag := null, #rn := 0;
select max(id),
functionario,
loja,
min(checkin),
max(checkout)
from (
select case when (checkinLag is null and checkin is not null) or
(checkinLag is not null and checkin is null)
then #rn := #rn + 1 else #rn end rn,
checkin,
checkout,
loja,
id,
functionario
from (
select #checkinLag checkinLag,
#checkinLag := checkin,
checkin,
checkout,
loja,
id,
functionario
from dummyTable
order by coalesce(checkin, checkout)
) a
) a group by functionario, loja, rn
I have used subqueries, to guarantee order of evaluating expressions (assigning and using of #checkinLag), as Gordon Linoff pointed.
Demo
My solution:
Select
*
from dummyTable base
where (base.checkout is null or not exists (
select
1
from dummyTable co
where co.checkout between base.checkout and DATE_ADD(base.checkout, INTERVAL 5 SECOND)
and base.id <> co.id
and base.functionario = co.functionario
and base.loja = co.loja
)) and (base.checkin is null or not exists (
select
1
from dummyTable ci
where ci.checkin between DATE_SUB(base.checkin, INTERVAL 5 SECOND) and base.checkin
and base.id <> ci.id
and base.functionario = ci.functionario
and base.loja = ci.loja
));
you can test the query here. There is no need that the rows are orderd. I choose 5 seconds as the interval where check-in/outs should be ignored.
How would I go about creating group_ids in the following example based on the area(s) the users are active in?
group_id rep_id area datebegin dateend
1 1000 A 1/1/15 1/1/16
1 1000 B 1/1/15 1/1/16
2 1000 C 1/2/16 12/31/99
In the table you can see that rep 1000 was active in both A and B between 1/15 and 1/16. How would I go about coding the group_id field to group by datebegin & dateend?
Thanks for any help.
You can use variables in order to enumerate groups of records having identical rep_id, datebegin, dateend values:
SELECT rep_id, datebegin, dateend,
#rn := IF(#rep_id <> rep_id,
IF(#rep_id := rep_id, 1, 1),
#rn + 1) AS rn
FROM (
SELECT rep_id, datebegin, dateend
FROM mytable
GROUP BY rep_id, datebegin, dateend) AS t
CROSS JOIN (SELECT #rep_id := 0, #rn := 0) AS v
ORDER BY rep_id, datebegin
Output:
rep_id, datebegin, dateend, rn
-----------------------------------
1000, 2015-01-01, 2016-01-01, 1
1000, 2016-02-01, 2099-12-03, 2
You can use the above query as a derived table and join back to the original table. rn field is the group_id field you are looking for.
You can use variables to assign groups. As you said, only if the date_begin and date_end exactly match for 2 rows, they would be in the same group. Else a new group starts.
select rep_id,area,date_begin,date_end,
,case when #repid <> rep_id then #rn:=1 --reset the group to 1 when rep_id changes
when #repid=rep_id and #begin=date_begin and #end=date_end then #rn:=#rn --if rep_id,date_begin and date_end match use the same #rn previously assigned
else #rn:=#rn+1 --else increment #rn by 1
end as group_id
,#begin:=date_begin
,#end:=date_end
,#repid:=rep_id
from t
cross join (select #rn:=0,#begin:='',#end:='',#repid:=-1) r
order by rep_id,date_begin,date_end
The above query includes variables in the output. To only get the group_id use
select rep_id,area,date_begin,date_end,group_id
from (
select rep_id,area,date_begin,date_end
,case when #repid <> rep_id then #rn:=1
when #repid=rep_id and #begin=date_begin and #end=date_end then #rn:=#rn
else #rn:=#rn+1
end as group_id
,#begin:=date_begin
,#end:=date_end
,#repid:=rep_id
from t
cross join (select #rn:=0,#begin:='',#end:='',#repid:=-1) r
order by rep_id,date_begin,date_end
) x
I'm not sure if the following can be done using a mere select statement, but I have two tables (truncated with the data necessary to the problem).
Inventory Item
id int (PRIMARY)
quantity int
Stock - Contains changes in the stock of the inventory item (stock history)
id int (PRIMARY)
inventory_item_id int (FOREIGN KEY)
quantity int
created datetime
The quantity in stock is the change in stock, while the quantity in inventory item is the current quantity of that item
EVERYTHING IN THE running COLUMN WILL RETURN 0
SELECT
inventory_item.id,
(inventory_item.quantity - SUM(stock.quantity)) AS running
FROM
stock
JOIN
inventory_item ON stock.inventory_item_id = inventory_item.id
GROUP BY inventory_item.id
THE QUESTION
Now, what I would like to know is: Is it possible to select all of the dates in the stock table where the running quantity of the inventory_item ever becomes zero using a SELECT?
I know this can be done programmatically by simply selecting all of the stock data in one item, and subtracting the stock quantity individually from the current inventory item quantity, which will get the quantity before the change in stock happened. Can I do this with a SELECT?
(Updated) Assuming there will never be more than one record for a given combination of inventory_item_id and created, try:
SELECT i.id,
s.created,
i.quantity - COALESCE(SUM(s2.quantity),0) AS running
FROM inventory_item i
JOIN stock s ON s.inventory_item_id = i.id
LEFT JOIN stock s2 ON s2.inventory_item_id = i.id and s.created < s2.created
GROUP BY i.id, s.created
HAVING running=0
My take on it:
select
inventory_item_id `item`,
created `when`
from
(select
#total := CASE WHEN #curr <> inventory_item_id
THEN quantity
ELSE #total+quantity END as running_total,
inventory_item_id,
created,
#curr := inventory_item_id
from
(select #total := 0) a
(select #curr := -1) b
(select inventory_item_id, created, quantity from stock order by inventory_item_id, created asc) c
) running_total
where running_total.running_total = 0;
This one has the relative advantage of having to give only one pass to the stock table. Depending on the size and the indexes on it that may or may not be a good thing.
The most logical way to do this is with a cumulative sum. But, MySQL doesn't support that.
The clearest approach, in my opinion, is to use a correlated subquery to get the running quantity. Then it is a simple matter of a where clause to select where it is 0:
select i.*
from (select i.*,
(select SUM(i2.inventory)
from inventory i2
where i2.inventory_item_id = i.inventory_item_id and
i2.created <= i.created
) as RunningQuantity
from inventory i
) i
where RunningQuantity = 0;
I had a response similar based on a running total to be flagged found here...
You can do with MySQL #variables, but the data needs to be pre-queried and ordered by the data of activity... then set a flag on each row that causes the negative and keep only those. Something like
select
PreQuery.*
from
( select
s.id,
s.created,
#runBal := if( s.id = #lastID, #runBal - quantity, #i.quantity ) as CurBal,
#lastID := s.id as IDToCompareNextEntry
from
stock s
join inventory_item ii
on s.inventory_item_id = ii.id,
(select #lastID := -1,
#runBal := 0 ) sqlvars
order by
s.id,
s.created DESC ) PreQuery
where
PreQuery.CurBal < 0
This way, for each inventory item, it works backwards by created date (order by the created descending per ID). So, when the inventory ID changes, look to the inventory table "Quantity" field to START the tally of used stock down. If same ID as the last record processed, just use the running balance and subtract out the quantity of that stock entry.
I believe this is a simple approach to this.
SELECT inventory_item.id, stock.created
FROM inventory_item
JOIN stock ON stock.inventory_item_id = inventory_item.id
WHERE (SELECT SUM(quantity) FROM stock WHERE created <= stock.created) = 0
There is a table with the columns :
USE 'table';
insert into person values
('11','xxx','1976-05-10','p1'),
('11','xxx ','1976-06-11','p1'),
('11','xxx ','1976-07-21','p2'),
('11','xxx ','1976-08-31','p2'),
Can anyone suggest me a query to get the start and the end date of the person with respect to the place he changed chronologically.
The query I wrote
SELECT PId,Name,min(Start_Date) as sdt, max(Start_Date) as edt, place
from **
group by Place;
only gives me the first two rows of my answer. Can anyone suggest the query??
This isn't pretty, and performance might be horrible, but at least it works:
select min(sdt), edt, place
from (
select A.Start_Date sdt, max(B.Start_Date) edt, A.place
from person A
inner join person B on A.place = B.place
and A.Start_Date <= B.Start_Date
left join person C on A.place != C.place
and A.Start_Date < C.Start_Date
and C.Start_Date < B.Start_Date
where C.place is null
group by A.Start_Date, A.place
) X
group by edt, place
The idea is that A and B represent all pairs of rows. C will be any row in between these two which has a different place. So after the C.place is null restriction, we know that A and B belong to the same range, i.e. a group of rows for one place with no other place in between them in chronological order. From all these pairs, we want to identify those with maximal range, those which encompass all others. We do so using two nested group by queries. The inner one will choose the maximal end date for every possible start date, whereas the outer one will choose the minimal start date for every possible end date. The result are maximal ranges of chronologically subsequent rows describing the same place.
This can be achived by:
SELECT Id, PId,
MIN(Start_Date) AS sdt,
MAX(Start_Date) as edt,
IF(`place` <> #var_place_prev, (#var_rank:= #var_rank + 1), #var_rank) AS rank,
(#var_place_prev := `place`) AS `place`
FROM person, (SELECT #var_rank := 0, #var_place_prev := "") dummy
GROUP BY rank, Place;
Example: SQLFiddle
If you want records to be ordered by ID then:
SELECT Id, PId,
MIN(Start_Date) AS sdt,
MAX(Start_Date) as edt,
`place`
FROM(
SELECT Id, PId,
Start_Date
IF(`place` <> #var_place_prev,(#var_rank:= #var_rank + 1),#var_rank) AS rank,
(#var_place_prev := `place`) AS `place`
FROM person, (SELECT #var_rank := 0, #var_place_prev := "") dummy
ORDER BY ID ASC
) a
GROUP BY rank, Place;
I have a table consisting of groups of, for example, five rows each. Each row in each group possesses a date value unique to that group.
What I want to do in my query, is go through the table, and increment a user variable (#count) when this date value changes. That's to say, #count should equal the group count, rather than the row count.
My current query looks like this, in case you're wondering:
SELECT #row := #row +1 AS rownum, date
FROM ( SELECT #row := 0 ) r, stats
Thanks a lot.
What about something like this?
SELECT
(CASE WHEN #date <> date THEN #row := #row +1 ELSE #row END) AS rownum,
#date:= date,
date
FROM ( SELECT #row := 0, #date := NOW() ) r, stats
You don't need a user variable to answer the query that you are doing. Is there a reason you want to use the user variable (for example, to emulate a ranking function?)
If not:
-- how many groups are there?
select count(distinct date) distinct_groups from table;
-- each group and count of rows in the group
select date, count(*) from table group by date;
-- if you want the Nth row from each group, assuming you have an auto_increment called id:
select *
from table
join ( select date, max(id) id
from table
group by date
) sq
on table.id = sq.id