I have 3 tables as below. What I need to do is create a sumamry after left joining the 1st table to the 2nd and the 2nd to the 3rd.
The code I'm using ends up resulting in a cartesian join. My query to create the 1st table (person) is complicated and resource intensive while the volume of data is table 2(shopping list) is massive so having a nested query is not ideal. Below is the code I'm using right now and the expected output (image 1) & what I get (image 2)
select
a.ID,
a.Name,
sum(b.cost) total_cost,
sum(c.discount_amount) total_discount
from
person a,
left join shopping_list b on a.id=b.id
left join discount c on b.item = c.item
group by
a.ID,
a.Name
I've looked at the below links but I was hoping there's a solution that may work better give the size of my dataset
https://dba.stackexchange.com/questions/217220/how-i-use-multiple-sum-with-multiple-left-joins
Multiple Left Join with sum
Thanks in advance for your help
You have multiple rows for the discounts, so presummarize those:
select p.id, p.name, coalesce(sl.cost, 0) as cost,
coalesce(d.discount_amount, 0) as discount_amount
from person p left join
shopping_list sl
on sl.id = p.id left join
(select d.item, sum(discount_amount) as discount_amount
from discount
group by d.item
) d
on sl.item = d.item
group by p.id, p.name;
The problem with your query is that the multiple rows of discount end up multiplying the rows of shopping_list -- resulting in the inaccurate totals.
Notice that in this query, the table aliases are abbreviations for the table names. This is a best practice that makes it much, much easier to follow the logic of a query.
Related
I have the following table resulted from
SELECT m.MedName as [Medicine],m.MedSellPrice as [RetailPrice],m.MedType as [Type],
m.SoldQuantity as [Sold],m.Quantity as [Available],b.BillAmount as [Total Bill],b.BillDate
FROM BillMedicine AS bm LEFT JOIN
Medicine AS m
ON bm.MedicineID=m.id LEFT JOIN
Bill AS b
ON bm.BilIID = b. ID
but now I want to remove the repeated rows except the Sum of 'TotalBill'.
Use GROUP BY:
SELECT
m.MedName AS [Medicine],
m.MedSellPrice AS [RetailPrice],
m.MedType AS [Type],
m.SoldQuantity AS [Sold],
m.Quantity AS [Available],
SUM(b.BillAmount) AS [Total Bill]
FROM BillMedicine AS bm
LEFT JOIN Medicine AS m
ON bm.MedicineID = m.id
LEFT JOIN Bill AS b
ON bm.BilIID = b.ID
GROUP BY
m.MedName,
m.MedSellPrice,
m.MedType,
m.SoldQuantity,
m.Quantity;
Note that for the billing date, the two "duplicate" records you have highlighted have different dates. It is not clear which date, if any, you want to report here. I have omitted this column.
GROUP BY Is Best Option for DUPLICATE DATE Removed & SUM.
Select Column1,column2....., SUM(Total) as Total From Tablename Group BY column1,column2
You seem to want most (or all) columns from m and then the sum from another table. One method is a lateral join or correlated subquery:
SELECT m.*, -- or whatever columns you want,
(SELECT SUM(b.BillAmount)
FROM BillMedicine bm JOIN
Bill b
ON bm.BilIID = b.ID
WHERE bm.MedicineID = m.id
) as [Total Bill]
FROM Medicine m ;
I suggest this approach for several reasons.
This is often more efficient than an outer aggregation.
You have LEFT JOINs but they do not look correct. I suspect you want to start with the Medicine table.
You are including a date/time in the results, but clearly that is not appropriate when combining multiple rows.
I have to make a list of customer who do not have any invoice but have paid an invoice … maybe twice.
But with my code (stated below) it contains everything from the left join. However I only need the lines highlighted with green.
How should I make a table with only the 2 highlights?
Select paymentsfrombank.invoicenumber,paymentsfrombank.customer,paymentsfrombank.value
FROM paymentsfrombank
LEFT OUTER JOIN debtors
ON debtors.value = paymentsfrombank.value
You only want to select columns from paymentsfrombank. So why do you even join?
select invoice_number, customer, value from paymentsfrombank
except
select invoice_number, customer, value from debtors;
(This requires exact matches as in your example, i.e. same amount for the invoice/customer).
There are two issues in your SQL. First, you need to join on Invoice number, not on value, as joining on value is pointless. Second, you need to only pick those payments where there are no corresponding debts, i.e. when you left-join, the table on the right has "null" in the joining column. The SQL would be something like this:
SELECT paymentsfrombank.invoicenumber,paymentsfrombank.customer,paymentsfrombank.value
FROM paymentsfrombank
LEFT OUTER JOIN debtors
ON debtors.InvoiceNumber = paymentsfrombank.InvoiceNumber
WHERE debtors.InvoiceNumber is NULL
in mysql we usually have this way to flip the relation and extract the rows that dosen't have relation.
Select paymentsfrombank.invoicenumber,paymentsfrombank.customer,paymentsfrombank.value
FROM paymentsfrombank
LEFT OUTER JOIN debtors
ON debtors.value = paymentsfrombank.value where debtors.value is null
You can use NOT EXISTS :
SELECT p.*
FROM paymentsfrombank p
WHERE NOT EXISTS (SELECT 1 FROM debtors d WHERE d.invoice_number = p.invoice_number);
However, the LEFT OUTER JOIN would also work if you add filtered with WHERE Clause to filtered out only missing customers that haven't any invoice information :
SELECT p.invoicenumber, p.customer, p.value
FROM paymentsfrombank P LEFT OUTER JOIN
debtors d
ON d.InvoiceNumber = p.InvoiceNumber
WHERE d.InvoiceNumber IS NULL;
Note : I have used table alias (p & d) that makes query to easier read & write.
I am using SQL Server to query these three tables that look like (there are some extra columns but not that relevant):
Customers -> Id, Name
Addresses -> Id, Street, StreetNo, CustomerId
Sales -> AddressId, Week, Total
And I would like to get the total sales per week and customer (showing at the same time the address details). I have come up with this query
SELECT a.Name, b.Street, b.StreetNo, c.Week, SUM (c.Total) as Total
FROM Customers a
INNER JOIN Addresses b ON a.Id = b.CustomerId
INNER JOIN Sales c ON b.Id = c.AddressId
GROUP BY a.Name, c.Week, b.Street, b.StreetNo
and even if my SQL skill are close to none it looks like it's doing its job. But now I would like to be able to show 0 whenever the one customer don't have sales for a particular week (weeks are just integers). And I wonder if somehow I should get distinct values of the weeks in the Sales table, and then loop through them (not sure how)
Any help?
Thanks
Use CROSS JOIN to generate the rows for all customers and weeks. Then use LEFT JOIN to bring in the data that is available:
SELECT c.Name, a.Street, a.StreetNo, w.Week,
COALESCE(SUM(s.Total), 0) as Total
FROM Customers c CROSS JOIN
(SELECT DISTINCT s.Week FROM sales s) w LEFT JOIN
Addresses a
ON c.CustomerId = a.CustomerId LEFT JOIN
Sales s
ON s.week = w.week AND s.AddressId = a.AddressId
GROUP BY c.Name, a.Street, a.StreetNo, w.Week;
Using table aliases is good, but the aliases should be abbreviations for the table names. So, a for Addresses not Customers.
You should generate a week numbers, rather than using DISTINCT. This is better in terms of performance and reliability. Then use a LEFT JOIN on the Sales table instead of an INNER JOIN:
SELECT a.Name
,b.Street
,b.StreetNo
,weeks.[Week]
,COALESCE(SUM(c.Total),0) as Total
FROM Customers a
INNER JOIN Addresses b ON a.Id = b.CustomerId
CROSS JOIN (
-- Generate a sequence of 52 integers (13 x 4)
SELECT ROW_NUMBER() OVER (ORDER BY a.x) AS [Week]
FROM (VALUES(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1),(1)) a(x)
CROSS JOIN (SELECT x FROM (VALUES(1),(1),(1),(1)) b(x)) b
) weeks
LEFT JOIN Sales c ON b.Id = c.AddressId AND c.[Week] = weeek.[Week]
GROUP BY a.Name
,b.Street
,b.StreetNo
,weeks.[Week]
Please try the following...
SELECT Name,
Street,
StreetNo,
Week,
SUM( CASE
WHEN Total IS NULL THEN
0
ELSE
Total
END ) AS Total
FROM Customers a
JOIN Addresses b ON a.Id = b.CustomerId
RIGHT JOIN Sales c ON b.Id = c.AddressId
GROUP BY a.Name,
c.Week,
b.Street,
b.StreetNo;
I have modified your statement in three places. The first is I changed your join to Sales to a RIGHT JOIN. This will join as it would with an INNER JOIN, but it will also keep the records from the table on the right side of the JOIN that do not have a matching record or group of records on the left, placing NULL values in the resulting dataset's fields that would have come from the left of the JOIN. A LEFT JOIN works in the same way, but with any extra records in the table on the left being retained.
I have removed the word INNER from your surviving INNER JOIN. Where JOIN is not preceded by a join type, an INNER JOIN is performed. Both JOIN and INNER JOIN are considered correct, but the prevailing protocol seems to be to leave the INNER out, where the RDBMS allows it to be left out (which SQL-Server does). Which you go with is still entirely up to you - I have left it out here for illustrative purposes.
The third change is that I have added a CASE statement that tests to see if the Total field contains a NULL value, which it will if there were no sales for that Customer for that Week. If it does then SUM() would return a NULL, so the CASE statement returns a 0 instead. If Total does not contain a NULL value, then the SUM() of all values of Total for that grouping is performed.
Please note that I am assuming that Total will not have any NULL values other than from the RIGHT JOIN. Please advise me if this assumption is incorrect.
Please also note that I have assumed that either there will be no missing Weeks for a Customer in the Sales table or that you are not interested in listing them if there are. Again, please advise me if this assumption is incorrect.
If you have any questions or comments, then please feel free to post a Comment accordingly.
I have a query:
SELECT
d.FiscalMonth,
d.FiscalMonthOfYear,
p.Name
FROM
DimDate d
LEFT JOIN FactSales f on f.SaleDate=d.PKDate
LEFT JOIN DimPerson p on p.PersonId=f.PersonId
WHERE d.FiscalYear='2014/7/1'
group by d.FiscalMonth, d.FiscalMonthOfYear, p.Name
ORDER BY d.FiscalMonthOfYear asc, p.PersonID asc
Which gives me these results:
Which is all fine, I want to include all months, even the ones that don't have data. (In this case FiscalMonth 2-12.)
The problem I have is with that one NULL value where I have data, IE. FiscalMonthOfYear 1. The red box.
How would I go about not returning that one "NULL" for the FiscalMonth=2014-07-01? I've tried some various where clauses but any time I remove the "NULL" values from the results, I also remove all the ones I want (IE. FiscalMonthOfYear 2-12)
Any help or guidance is greatly appreciated!
Thanks!
-Russ
Update:
DimDate table has primary key PKDate, which is one row for every date:
DimDate
PKDate ....
2014-07-01
2014-07-02
2014-07-03
etc.
FaceSales table has one ore many Sales transactions for a given day:
FactSales
SaleDate Amount
2014-07-01 34.99
2014-07-01 21.89
2014-07-02 24.77
2014-07-04 22.77
The problem is that FactSales may not have a sale on a particular day. So my query is finding that one (or many) days with no transactions, and because of the LEFT JOIN is returning it. How would I go about removing this result so it's not in my results?
SELECT
d.PKDate
,f.SaleDate
FROM
DimDate d
LEFT JOIN FactSales f on f.SaleDate=d.PKDate
LEFT JOIN DimPerson p on p.PersonId=f.PersonId
WHERE d.FiscalYear='2014/7/1'
ORDER BY d.PKDate
The problems stems from the fact that you are actually trying to do two things at once:
You want all the Names related to sales of fiscal months with at
least one sale
You want an extra row for all fiscal month with no
sales
As often goes in these cases... you should solve the two distinct problems and then put together the results (with a UNION in this specific case).
Something like this:
SELECT * FROM
(
SELECT DISTINCT
d.FiscalMonth,
d.FiscalMonthOfYear,
p.Name
FROM DimDate d
JOIN FactSales f ON f.SaleDate=d.PKDate
JOIN DimPerson p ON p.PersonId=f.PersonId
WHERE d.FiscalYear='2014/7/1'
) UNION (
SELECT
d.FiscalMonth,
d.FiscalMonthOfYear,
NULL AS Name
FROM DimDate d
LEFT JOIN FactSales f ON f.SaleDate=d.PKDate
WHERE d.FiscalYear='2014/7/1'
GROUP BY d.FiscalMonth, d.FiscalMonthOfYear, p.Name
HAVING COUNT(f.SaleDate)=0
)
ORDER BY FiscalMonthOfYear asc, PersonID ASC
I haven't tested it, and there may be some better ways to solve the second part (SUBSELECT, EXISTS) but that depends a bit on the engine you are using.
You can do an inner join as follows:
SELECT
d.FiscalMonth,
d.FiscalMonthOfYear,
p.Name
FROM
DimDate d
INNER JOIN FactSales f on f.SaleDate=d.PKDate
LEFT JOIN DimPerson p on p.PersonId=f.PersonId
WHERE d.FiscalYear='2014/7/1'
group by d.FiscalMonth, d.FiscalMonthOfYear, p.Name
ORDER BY d.FiscalMonthOfYear asc, p.PersonID asc
The inner join does a union of the two tables without giving priority to the left table. For more on joins you can read this blog: Visual representation of sql joins
Which states that an INNER JOIN will return all of the records in the left table (table A) that have a matching record in the right table (table B) whearas a LEFT JOIN will return all of the records in the left table (table A) regardless if any of those records have a match in the right table (table B)
Im working myself into an SQL frenzy, hopefully someone out there can help!
I've got 2 tables which are basically Records and Outcomes, I want to join the 2 tables together, count the number of outcomes per record (0 or more) which I've got quite easily with:
Select records.Id, (IsNull(Count(outcomes.Id),0)) as outcomes
from records
Left Join
outcomes
on records.Id = outcomes.Id
group by
records.Id
The outcomes table also has a timestamp in it, what I want to do is include the last outcome in my result set, if I add that the my query it generates a record for every combination of records to outcomes.
Can any SQL expert point me in the right direction?
Cheers,
try:
SELECT
dt.Id, dt.outcomes,MAX(o.YourTimestampColumn) AS LastOne
FROM (SELECT --basically your original query, just indented differently
records.Id, (ISNULL(COUNT(outcomes.Id),0)) AS outcomes
from records
LEFT JOIN outcomes ON records.Id = outcomes.Id
GROUP BY records.Id
) dt
INNER JOIN outcomes o ON dt.Id = o.Id
GROUP BY dt.Id, dt.outcomes