Here is my SQL command :
SELECT
ts.CHECK_NUMBER,
ts.CUSTOMER_NAME,
ts.COMPANY_NAME,
( SELECT COUNT(*)
FROM TRANSACTION_ORDER too
WHERE too.CHECK_NUMBER = ts.CHECK_NUMBER
) as NB_OF_ORDERS
FROM
TRANSACTION_SUMMARY ts
ORDER BY
ts.BUSINESS_DATE
It is taking so long to render data, we are talking about minimum 3000 transactions, for each one we have to count the orders.
Is there any better solution?
It is taking too long because when you have this sub-query in your select , it is executed for each row returned by the outer query, so if your outer query returns 50,000 rows this inner select query will be executed 50,000 times which is obviously a performance killer,
You should try something like this....
SELECT
ts.CHECK_NUMBER
,ts.CUSTOMER_NAME
,ts.COMPANY_NAME
,ISNULL(O.Total, 0) AS NB_OF_ORDERS
FROM TRANSACTION_SUMMARY ts
LEFT JOIN --<-- use inner join is you only want records with some orders
( SELECT CHECK_NUMBER, COUNT(*) AS Total
FROM TRANSACTION_ORDER
GROUP BY CHECK_NUMBER
) as O
ON ts.CHECK_NUMBER = O.CHECK_NUMBER
ORDER BY ts.BUSINESS_DATE
Related
I have a query that returns the following data:
I am trying to adapt it to sum the total number of runs at each venue. I have come up with the query below but there are two issues:
it is not summing by venue it is summing all runs;
it takes a very long time to run.
Can anyone see what I'm doing wrong?
Thanks
SELECT ScorecardBatting.matchId, ScorecardBatting.battingTeam, ScorecardBatting.inningsNo, ScorecardBatting.batsmanId, ScorecardBatting.howDismissed, ScorecardBatting.runs, ScorecardBatting.ballsFaced, Matches.venue, (SELECT SUM(runs) FROM ScorecardBatting WHERE Matches.venue=Matches.venue) AS TOTAL
FROM Matches INNER JOIN ScorecardBatting ON Matches.matchId = ScorecardBatting.matchId
GROUP BY ScorecardBatting.matchId, ScorecardBatting.battingTeam, ScorecardBatting.inningsNo, ScorecardBatting.batsmanId, ScorecardBatting.howDismissed, ScorecardBatting.runs, ScorecardBatting.ballsFaced, Matches.venue;
If you want the total number of runs for each venue, then a simple aggregation query does what you want:
SELECT Matches.venue, SUM(runs) AS TOTAL
FROM Matches INNER JOIN
ScorecardBatting
ON Matches.matchId = ScorecardBatting.matchId
GROUP BY Matches.venue;
If you want this in your original query, you could join it in:
select . . ., t.total
from Matches inner join
ScorecardBatting
on Matches.matchId = ScorecardBatting.matchId join
(select Matches.venue, sum(runs) AS TOTAL
from Matches INNER JOIN
ScorecardBatting
on Matches.matchId = ScorecardBatting.matchId
group by Matches.venue
) t
on t.venue = matches.venue;
I don't think you need a group by fro your query.
I have three tables in Access:
employees
----------------------------------
id (pk),name
times
----------------------
id (pk),employee_id,event_time
time_notes
----------------------
id (pk),time_id,note
I want to get the record for each employee record from the times table with an event_time immediately prior to some time. Doing that is simple enough with this:
select employees.id, employees.name,
(select top 1 times.id from times where times.employee_id=employees.id and times.event_time<=#2018-01-30 14:21:48# ORDER BY times.event_time DESC) as time_id
from employees
However, I also want to get some indication of whether there's a matching record in the time_notes table:
select employees.id, employees.name,
(select top 1 time_notes.id from time_notes where time_notes.time_id=(select top 1 times.id from times where times.employee_id=employees.id and times.event_time<=#2018-01-30 14:21:48# ORDER BY times.event_time DESC)) as time_note_present,
(select top 1 times.id from times where times.employee_id=employees.id and times.event_time<=#2018-01-30 14:21:48# ORDER BY times.event_time DESC) as last_time_id
from employees
This does work but it's SOOOOO SLOW. We're talking 10 seconds or more if there's 100 records in the employee table. The problem is peculiar to Access as I can't use the last_time_id result of the other sub-query like I can in MySQL or SQL Server.
I am looking for tips on how to speed this up. Either a different query, indexes. Something.
Not sure if something like this would work for you?
SELECT
employees.id,
employees.name,
time_notes.id AS time_note_present,
times.id AS last_time_id
FROM
(
employees LEFT JOIN
(
times INNER JOIN
(
SELECT times.employee_id AS lt_employee_id, max(times.event_time) AS lt_event_time
FROM times
WHERE times.event_time <= #2018-01-30 14:21:48#
GROUP BY times.employee_id
)
AS last_times
ON times.event_time = last_times.lt_event_time AND times.employee_id = last_times.lt_employee_id
)
ON employees.id = times.employee_id
)
LEFT JOIN time_notes ON times.id = time_notes.time_id;
(Completely untested and may contain typos)
Basically, your query is running multiple correlated subqueries even a nested one in a WHERE clause. Correlated queries calculate a value separately for each row, corresponding to outer query.
Similar to #LeeMac, simply join all your tables to an aggregate query for the max event_time grouped by employee_id which will run once across all rows. Below times is the baseFROM table joined to the aggregate query, employees, and time_notes tables:
select e.id, e.name, t.event_time, n.note
from ((times t
inner join
(select sub.employee_id, max(sub.event_time) as max_event_time
from times sub
where sub.event_time <= #2018-01-30 14:21:48#
group by sub.employee_id
) as agg_qry
on t.employee_id = agg_qry.employee_id and t.event_time = agg_qry.max_event_time)
inner join employees e
on e.id = t.employee_id)
left join time_notes n
on n.time_id = t.id
I need to limit the results of my query so that it only pulls results where the total number of lines on the ID is less than 4, and am unsure how to do this without losing the select statement columns.
select fje.journalID, fjei.ItemID, fjei.acccount, fjei.debit, fjei.credit
from JournalEntry fje
inner join JournalEntryItem fjei on fjei.journalID = fje.journalID
inner join JournalEntryItem fjei2 on fjei.journalID = fjei2.journalID and
fjei.ItemID != fjei2.ItemID
order by fje.journalID
So if journalID 1 has 5 lines, it should be excluded, but if it has 4 lines, I should see it in my query. Just need a push in the right direction. Thanks!
A subquery with an alias has many names, but it's effectively a table. In your case, you would do something like this.
select your fields
from your tables
join (
select id, count(*) records
from wherever
group by id ) derivedTable on someTable.id = derivedTable.id
and records < 4
I am trying to speed up my execution time. What's wrong with my query. What is the better way to do query optimization.
TransactionEntry has 2 Million records
Transaction Table has 5 Billion Records
Here is my Query, If I remove the TotalPrice column, I am getting results at 10sec
--Total Quantity
SELECT
items.ItemLookupCode,sum(transactionsEntry.Quantity) Quantity,sum(transactionsEntry.Quantity*transactionsEntry.Price) TotalPrice
into
##temp_TotalPrice
FROM
(
SELECT
TransactionNumber,StoreID,Time
FROM
[HQMatajer].[dbo].[Transaction]
WHERE
Time>=CONVERT(datetime,'2015-01-01 00:00:00',102) and Time<=CONVERT(datetime,'2015-12-31 23:59:59',102)
) transactions
left join [HQMatajer].[dbo].[TransactionEntry] transactionsEntry
ON transactionsEntry.TransactionNumber=transactions.TransactionNumber and transactionsEntry.StoreID=transactions.StoreID
Left join [HQMatajer].[dbo].[Item] items
ON transactionsEntry.ItemID=items.ID
Group By items.ItemLookupCode
Order by items.ItemLookupCode
If I execute this(above one) query, it produce the result in 22 seconds. It's too long
When I execute the subquery alone(Below one). It's taking 11 seconds
(
SELECT
TransactionNumber,StoreID,Time
FROM
[HQMatajer].[dbo].[Transaction]
WHERE
Time>=CONVERT(datetime,'2015-01-01 00:00:00',102) and Time<=CONVERT(datetime,'2015-12-31 23:59:59',102)
) transactions
I have created one index for TransactionEntry Table that
TransactionNumber,StoreID,ItemID,Quantity,Price
One index for Transaction Table
`Time,TransactionNumber,StoreID`
One Index for Item Table
`ID`
Execution Plan
Clustured Index of TransactionEntry is taking 59% cost. That column_Name is AutoID
Assuming this is for SQL 2005 or above version. If its for SQL 2000, then instead of CTE you can have a temp table with proper index.
Also Since you were getting the values from [HQMatajer].[dbo].[TransactionEntry] and [HQMatajer].[dbo].[Item], why Left Join is used?
Avoid sub queries. I have re framed the query. Please check and let me know whether it improved the performance
;WITH transactions
AS
(
SELECT
TransactionNumber,StoreID,Time
FROM
[HQMatajer].[dbo].[Transaction]
WHERE
Time>=CONVERT(datetime,'2015-01-01 00:00:00',102) and Time<=CONVERT(datetime,'2015-12-31 23:59:59',102)
)
SELECT
items.ItemLookupCode,sum(transactionsEntry.Quantity) Quantity,sum(transactionsEntry.Quantity*transactionsEntry.Price) TotalPrice
into
##temp_TotalPrice
FROM [HQMatajer].[dbo].[Item] items INNER JOIN [HQMatajer].[dbo].[TransactionEntry] transactionsEntry
ON transactionsEntry.ItemID=items.ID
WHERE EXISTS (SELECT 1 FROM transactions WHERE transactionsEntry.TransactionNumber=transactions.TransactionNumber and transactionsEntry.StoreID=transactions.StoreID)
Group By items.ItemLookupCode
Order by items.ItemLookupCode
This is your query, simplified and formatted a bit (the subquery makes no difference):
select i.ItemLookupCode,
sum(te.Quantity) as quantity,
sum(te.Quantity * te.Price) as TotalPrice
into ##temp_TotalPrice
from [HQMatajer].[dbo].[Transaction] t left join
[HQMatajer].[dbo].[TransactionEntry] te
on te.TransactionNumber = t.TransactionNumber and
te.StoreID = t.StoreID left join
[HQMatajer].[dbo].[Item] i
on te.ItemID = i.ID
where t.Time >= '2015-01-01' and
t.Time < '2016-01-01'
group by i.ItemLookupCode
order by i.ItemLookupCode;
For this query, you want indexes on Transaction(Time, TransactionNumber, StoreId), TransactionEntry(TransactionNumber, StoreId, ItemId, Quantity, Price), and Item(Id, ItemLookupCode)`.
Even with the right indexes, this is processing a lot of data, so I would be surprised if this reduced the time to a few seconds.
This query is taking to much time because three times the entry is inserted into the temporary table which increases the time. if we insert the record into a another table and thn call it or make it as a cte. It decreases the cost.
I have a query for pulling customer information, and I'm adding an max() function to find the most recent order date. Without the aggregate the query takes .23 seconds to run, but with it it takes 12.75 seconds.
Here's the query:
SELECT U.SEQ, MAX(O.ORDER_DATE) FROM CUST_MST U
INNER JOIN ORD_MST O ON U.SEQ = O.CUST_NUM
WHERE U.SEQ = :customerNumber
GROUP BY U.SEQ;
ORD_MST is a table with 890,000 records.
Is there a more efficient way to get this functionality?
EDIT: For the record, there's nothing specifically stopping me from running two queries and joining them in my program. I find it incredibly odd that such a simple query would take this long to run. In this case it is much cleaner/easier to let the database do the joining of information, but it's not the only way for me to get it done.
EDIT 2: As requested, here are the plans for the queries I reference in this question.
With Aggregate
Without Aggregate
the problem with your query is that you join both tables completely, then the max function is executed against the whole result, and at last the where statement filters your rows.
you have improve the join, by just joining the rows with the certain custid instead of the full tables, should look like this:
SELECT U.SEQ, MAX(O.ORDER_DATE) FROM
(SELECT * FROM CUST_MST WHERE SEQ = :customerNumber ) U
INNER JOIN
(SELECT * FROM ORD_MST WHERE CUST_NUM = :customerNumber) O ON U.SEQ = O.CUST_NUM
GROUP BY U.SEQ;
Another option is to use an order by and filter the first rownum. its not rly the clean way. Could be faster, if not you will also need a subselect to not order the full tables. Didnt use oracle for a while but it should look something like this:
SELECT * FROM
(
SELECT U.SEQ, O.ORDER_DATE FROM CUST_MST U
INNER JOIN ORD_MST O ON U.SEQ = O.CUST_NUM
WHERE U.SEQ = :customerNumber
GROUP BY U.SEQ;
ORDER BY O.ORDER_DATE DESC
)
WHERE ROWNUM = 1
Are you forced to use the join for some reason or why dont you select directly from ORD_MST without join?
EDIT
One more idea:
SELECT * FROM
(SELECT CUST_NUM, MAX(ORDER_DATE) FROM ORD_MST WHERE CUST_NUM = :customerNumber GROUP BY CUST_NUM) O
INNER JOIN CUST_MST U ON O.CUST_NUM = U.SEQ
if the inner select just takes one second, then the join should work instant.
Run this commands:
Explain plan for
SELECT U.SEQ, MAX(O.ORDER_DATE) FROM CUST_MST U
INNER JOIN ORD_MST O ON U.SEQ = O.CUST_NUM
WHERE U.SEQ = :customerNumber
GROUP BY U.SEQ;
select * from table( dbms_xplan.display );
and post results here.
Whithout knowing an execution plan we can only guess what really happens.
Btw. my feeling is that adding composite index for ORD_MST table with columns cust_num+order_date could solve the problem (assuming that SEQ is primary key for CUST_MST table and it has already an unique index). Try:
CREATE INDEX idx_name ON ORD_MST( cust_num, order_date );
Also, after creating the index refresh statistics with commands:
EXEC DBMS_STATS.gather_table_stats('your-schema-name', 'CUST_MST');
EXEC DBMS_STATS.gather_table_stats('your-schema-name', 'ORD_MST');
try your query.