SQL case operation - sql

Im fairly new with sql, and been trying to solve a problem where you have a table information about orders. In this case, Im trying to use the case operation to get a monthly report on orders, so I should have a column which states the year,another one which states the month, and then I should have columns for days 1-20,21-22,23-24 and above 25. Im trying to use the case operation to get the amount of orders that happened on those days.
I tried the following query :
SELECT
DATEPART(YEAR,date) AS year,DATEPART(MONTH,date) AS month,
COUNT(CASE WHEN DATEPART(DAY,date) BETWEEN 1 AND 20 THEN order ELSE 0 END) AS D1_D20,
COUNT(CASE WHEN DATEPART(DAY,date) BETWEEN 21 AND 22 THEN order ELSE 0 END) AS D21_D22,
COUNT(CASE WHEN DATEPART(DAY,date) BETWEEN 23 AND 24 THEN order ELSE 0 END) AS D23_D24,
COUNT(CASE WHEN DATEPART(DAY,date) > 25 THEN order ELSE 0 END) AS D25_END
FROM ORDERS
GROUP BY DATEPART(YEAR,date),DATEPART(MONTH,date)
Obviously the problem with that query is that, now I just get the total number of orders for each of the days, I know I should count the orders, but dont know the syntax. Help would be greatly appreciated!

Use SUM():
SELECT
DATEPART(YEAR, date) AS year, DATEPART(MONTH, date) AS month,
SUM(CASE WHEN DATEPART(DAY,date) BETWEEN 1 AND 20 THEN 1 ELSE 0 END) AS D1_D20,
SUM(CASE WHEN DATEPART(DAY,date) BETWEEN 21 AND 22 THEN 1 ELSE 0 END) AS D21_D22,
SUM(CASE WHEN DATEPART(DAY,date) BETWEEN 23 AND 24 THEN 1 ELSE 0 END) AS D23_D24,
SUM(CASE WHEN DATEPART(DAY,date) > 25 THEN 1 ELSE 0 END) AS D25_END
FROM ORDERS
GROUP BY DATEPART(YEAR, date), DATEPART(MONTH, date);
I would recommend using the functions DAY(), YEAR(), and MONTH() because they are simpler to type.
By the way, you can use COUNT() if you remove the ELSE clause. Your particular problem is that COUNT(0) = COUNT(1) because COUNT() counts non-NULL values. I prefer SUM() because it is more intuitive in this respect.

Related

Query to show all months and show values where there are data for the corresponding months

I have a query and it shows the months where there is corresponding data. However, I would like to show all of the months in the year and have the months where there are no data shown as zero.
There is my SQL Statement:
SELECT DATENAME(MONTH, hb_Disputes.OPENED) AS MonthValue,
COUNT(CASE WHEN REV_CLS = 2 THEN 1 END) AS SmallCommercialIndust,
COUNT(CASE WHEN REV_CLS <> 2 THEN 1 END) AS Residential
FROM hb_Disputes
WHERE (hb_Disputes.ASSGNTO = 'E099255') AND (YEAR(hb_Disputes.OPENED) = YEAR(GETDATE()))
GROUP BY hb_Disputes.OPENED
And this is my output:
I also have a table name MonthName that shows all of the months in a year and I know I may need to use this to accomplish what I'm trying to achieve but I'm not sure how to get there:
If you have data in the table for all months, but the where clause is filtering it out, then the simplest method is to extend the conditional aggregation:
SELECT DATENAME(MONTH, d.OPENED) AS MonthValue,
SUM(CASE WHEN d.ASSGNTO = 'E099255' AND d.REV_CLS = 2 THEN 1 ELSE 0 END) AS SmallCommercialIndust,
SUM(CASE WHEN d.ASSGNTO = 'E099255' AND d.REV_CLS <> 2 THEN 1 ELSE 0 END) AS Residential
FROM hb_Disputes d
WHERE YEAR(d.OPENED) = YEAR(GETDATE())
GROUP BY DATENAME(MONTH, d.OPENED)
ORDER BY MIN(d.OPENED);
Note: This does not fix the issue in all cases. It should just be a simple way to modify your query -- and will often work.

How to handle aggregate function in Case statements when it involves date columns

I'm calculating invoiceDate vs currentDate then sum Value/Amount column grouping by Customer but its returning "invoiceDate is not contained in either an aggregate function or the GROUP BY clause"
select Customer
,case
when datediff(dd,InvoiceDate,getdate()) <=30 then sum(InvoiceBal1)
else 0
end as [Current]
,case
when datediff(dd,InvoiceDate,getdate()) between 31 and 60 then sum(InvoiceBal1)
else 0
end as [30 Days]
from CusInvoice
group by Customer
You want conditional aggregation:
select Customer
sum(case when datediff(day, InvoiceDate, getdate()) <= 30
then InvoiceBal1 else 0
end) as balance_current
sum(case when datediff(day, InvoiceDate, getdate()) between 31 and 60
then InvoiceBal1 else 0
end) as balance_30days
from CusInvoice
group by Customer

Difference between COUNT and SUM within an Aggregate CASE statement

Full disclosure, I am learning and I have searched all over the internet and I just can't figure out my question.
I am working on an online class and was given the following example:
select
DATENAME(MONTH, DATEADD(MONTH, MONTH(OrderDate), -1)) AS 'Month',
SUM(CASE WHEN YEAR(OrderDate) = 2005 THEN 1 ELSE 0 END) AS Orders,
SUM(CASE YEAR(OrderDate) WHEN 2005 THEN Totaldue ELSE 0 END) AS 'Total Value'
from
sales.salesorderheader
group by Month(orderdate)
order by Month(orderdate) ASC
That returns the following results:
I understood that (I thought) so I began messing around with the code to further understand Case statements. Looking at the code I thought that the Orders field was essentially finding all the orders in a month, assigning a 1 to each one, and then adding them all up. Because each one was assigned a 1 I figured that I could change the SUM to COUNT and I would get the same results.
However, this code:
select
DATENAME(MONTH, DATEADD(MONTH, MONTH(OrderDate), -1)) AS 'Month',
COUNT(CASE WHEN YEAR(OrderDate) = 2005 THEN 1 ELSE 0 END) AS Orders,
SUM(CASE YEAR(OrderDate) WHEN 2005 THEN Totaldue ELSE 0 END) AS 'Total Value'
from
sales.salesorderheader
group by Month(orderdate)
order by Month(orderdate) ASC
Returns these results:
To try and break this down I created a query that would just look for the orders in January 2005 and count them.
SELECT COUNT(*)
FROM Sales.SalesOrderHeader
WHERE OrderDate >= '1/1/2005' AND OrderDate < '1/1/2005'
This returned 0. The same as the SUM query. I get that COUNT counts rows and SUM sums numbers in a column, but I just don't understand the results I'm getting. Could someone please explain why the count query is returning 2483 for January and not 0?
For COUNT 1 and 0 are the same. What you really need is NULL:
COUNT(ALL expression) evaluates expression for each row in a group and returns the number of nonnull values.
select
DATENAME(MONTH, DATEADD(MONTH, MONTH(OrderDate), -1)) AS 'Month',
COUNT(CASE WHEN YEAR(OrderDate) = 2005 THEN 1 ELSE NULL END) AS Orders,
SUM(CASE YEAR(OrderDate) WHEN 2005 THEN Totaldue ELSE 0 END) AS 'Total Value'
from sales.salesorderheader
group by Month(orderdate)
order by Month(orderdate) ASC;
Or even shorter(default ELSE is NULL so we could omit that part)
COUNT(CASE WHEN YEAR(OrderDate) = 2005 THEN 1 END) AS Orders,
Example:
SUM COUNT COUNT
2005 1 1 1
2006 0 0 NULL
2007 0 0 NULL
2005 1 1 1
===============================================
2 4 2
When you use count(*) you count ALL the rows. If you want to count how many orders you have, you have to use a column: eg: count(OrderDate). Try it
count example:
assume that your column has 3 value and column name is the order
2 ---------- 5 ---------- 4----- Null
now if you run
count (order)
it will return = 3 how many entries you have in the column without null
sum example:
2 ---------- 5 ---------- 4
now if you run
sum (order)
it will return = 2+5+4=11 its add all the entries

SQL Efficiency on Date Range or Separate Tables

I'm calculating historical amount from a table in years(ex. 2015-2016, 2014-2015, etc.) I would like to seek expertise if its more efficient to do it in one batch or repeat the query multiple times filtered by the date required.
Thanks in advance!
OPTION 1:
select
id,
sum(case when year(getdate()) - year(txndate) between 5 and 6 then amt else 0 end) as amt_6_5,
...
sum(case when year(getdate()) - year(txndate) between 0 and 1 then amt else 0 end) as amt_1_0,
from
mytable
group by
id
OPTION 2:
select
id, sum(amt) as amt_6_5
from
mytable
group by
id
where
year(getdate()) - year(txndate) between 5 and 6
...
select
id, sum(amt) as amt_1_0
from
mytable
group by
id
where
year(getdate()) - year(txndate) between 0 and 1
1.
Unless you have resources issues I would go with the CASE version.
Although it has no impact on the results, filtering on the requested period in the WHERE clause might have a significant performance advantage.
2. Your period definition creates overlapping.
select id
,sum(case when year(getdate()) - year(txndate) = 6 then amt else 0 end) as amt_6
-- ...
,sum(case when year(getdate()) - year(txndate) = 0 then amt else 0 end) as amt_0
where txndate >= dateadd(year, datediff(year,0, getDate())-6, 0)
from mytable
group by id
This may be help you,
WITH CTE
AS
(
SELECT id,
(CASE WHEN year(getdate()) - year(txndate) BETWEEN 5 AND 6 THEN 'year_5-6'
WHEN year(getdate()) - year(txndate) BETWEEN 4 AND 5 THEN 'year_4-5'
...
END) AS my_year,
amt
FROM mytable
)
SELECT id,my_year,sum(amt)
FROM CTE
GROUP BY id,my_year
Here, inside the CTE, just assigned a proper year_tag for each records (based on your conditions), after that select a summary for the CTE grouped by that year_tag.

Using multiple sum case lines in query

This code does exactly what I need it to do for the desired months. Basically provides Numerator and Denominator.
SUM(CASE WHEN smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date BETWEEN '2013-01-01' and '2013-01-31' THEN 1 ELSE 0 END) AS Total_Jan13,
SUM(CASE WHEN smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date BETWEEN '2013-01-01' and '2013-01-31' and [ind_ra_cfvmc_00-30] = 'YES' THEN 1 ELSE 0 END) AS RA_Jan13,
SUM(CASE WHEN smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date BETWEEN '2013-02-01' and '2013-02-28' THEN 1 ELSE 0 END) AS Total_Feb13,
SUM(CASE WHEN smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date BETWEEN '2013-02-01' and '2013-02-28' and [ind_ra_cfvmc_00-30] = 'YES' THEN 1 ELSE 0 END) AS RA_Feb13,
SUM(CASE WHEN smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date BETWEEN '2013-03-01' and '2013-03-31' THEN 1 ELSE 0 END) AS Total_Mar13,
It can get pretty tedious when you have multiple months...is there a more efficient way of performing this calculation?
THanks!
You could group them by the year and month in a sub-select and then manipulate that:
SELECT DATEPART(year, smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date) AS TotalYear,
DATEPART(month, smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date) AS TotalMonth,
COUNT(*) AS Total
FROM [table]
GROUP BY DATEPART(year, smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date),
DATEPART(month, smsdss.c_cfv_pas_fct_pt_acct_vst_all.vst_end_date)
and that would give you the totals by month, without having to specify the months beforehand.