I'm attempting to generate a list of vehicles that don't have a price or mileage listed using the below query. When I attempt to run the query, I get an error "ORA-00936: missing expression", but can't seem to find out why. From other posts here, I can see that using IS NULL should be the appropriate term for the WHEN portion, but I am not seeing anything wrong with the query itself. Any help would be appreciated!
Select
SUM(CASE vehicles.mileage WHEN IS NULL THEN 1 ELSE 0 END) NO_MILEAGE,
SUM(CASE vehicles.price WHEN IS NULL THEN 1 ELSE 0 END) NO_PRICE
From
[data]
Simple syntax error:
Select
SUM(CASE WHEN vehicles.mileage IS NULL THEN 1 ELSE 0 END) NO_MILEAGE,
SUM(CASE WHEN vehicles.price IS NULL THEN 1 ELSE 0 END) NO_PRICE
From
[data];
This is assuming a table named vehicles in your FROM clause or a columns with an object or nested table type in [data] named vehicles. Else the qualification vehicles. would not make sense.
Use a "searched" CASE for a decision between two alternatives.
Details about "simple" and "searched" CASE in the Oracle online reference.
You can also use COUNT for your particular case. The online reference again:
If you specify expr, then COUNT returns the number of rows where expr is not null.
If you specify the asterisk (*), then this function returns all rows,
including duplicates and nulls. COUNT never returns null.
So you need the difference:
Select
COUNT(*) - COUNT(vehicles.mileage) AS NO_MILEAGE,
COUNT(*) - COUNT(vehicles.price) AS NO_PRICE
From
[data];
You could also use Oracle's NVL2 function:
Select
SUM(NVL2(vehicles.mileage, 0, 1)) NO_MILEAGE,
SUM(NVL2(vehicles.price, 0, 1)) NO_PRICE
From
[data]
Related
SELECT
SP.SITE,
SYS.COMPANY,
SYS.ADDRESS,
SP.CUSTOMER,
SP.STATUS,
DATEDIFF(MONTH,SP.MEMBERSINCE, SP.EXPIRES) AS MONTH_COUNT
CASE WHEN(MONTH_COUNT = 0 THEN MONTH_COUNT = DATEDIFF(DAY,SP.MEMBERSINCE, SP.EXPIRES) AS DAY_COUNT)
ELSE NULL
END
FROM SALEPASSES AS SP
INNER JOIN SYSTEM AS SYS ON SYS.SITE = SP.SITE
WHERE STATUS IN (7,27,29);
I am still trying to understand SQL. Is this the right order to have everything? I'm assuming my datediff() is unable to work because it's inside case when. What I am trying to do, is get the day count if month_count is less than 1 (meaning it's less than one month and we need to count the days between the dates instead). I need month_count to run first to see if doing the day_count would even be necessary. Please give me feedback, I'm new and trying to learn!
Case is an expression, it returns a value, it looks like you should be doing this:
DAY_COUNT =
CASE WHEN DATEDIFF(MONTH,SP.MEMBERSINCE, SP.EXPIRES) = 0
THEN DATEDIFF(DAY,SP.MEMBERSINCE, SP.EXPIRES))
ELSE NULL END
You shouldn't actually need else null as NULL is the default.
Note also you [usually] cannot refer to a derived column in the same select
It appears that what you are trying to do is define the MonthCount column's value, and then reuse that value in another column's definition. (The Don't Repeat Yourself principle.)
In most dialects of SQL, you can't do that. Including MS SQL Server.
That's because SQL is a "declarative" language. This means that SQL Server is free to calculate the column values in any order that it likes. In turn, that means you're not allowed to do anything that would rely on one column being calculated before another.
There are two basic ways around that...
First, use CTEs or sub-queries to create two different "scopes", allowing you to define MonthCount before DayCount, and so reuse the value without retyping the definition.
SELECT
*,
CASE WHEN MonthCount = 0 THEN foo ELSE NULL END AS DayCount
FROM
(
SELECT
*,
bar AS MonthCount
FROM
x
)
AS derive_month
The second main way is to somehow derive the value Before the SELECT block is evaluated. In this case, using APPLY to 'join' a single value on to each input row...
SELECT
x.*,
MonthCount,
CASE WHEN MonthCount = 0 THEN foo ELSE NULL END AS DayCount
FROM
x
CROSS APPLY
(
SELECT
bar AS MonthCount
)
AS derive_month
Table 1, is a list of clients, what membership they have, what service they used, and the date the service was used
Table 2, is just table 1 grouped by month and membership type, then a count of the service sessions
What I am trying to do is count membership sessions only by particular service types. This is what I have so far, it returns an error saying 'Service_Type' is not in an aggregate function or group by clause, when I put 'Service_Type' in a group by, the query has no errors but the SESSIONS column is all NULL.
SELECT
DATEFROMPARTS(YEAR(t1.Date),MONTH(t1.Date),1)AS 'Draft_Date',
Membership,
CASE
WHEN Membership = 5 AND Service_Type = 'A' THEN COUNT(*)
WHEN Membership = 2 AND Service_Type IN ('J','C')
END AS'SESSIONS'
FROM Table1 t1
GROUP BY DATEFROMPARTS(YEAR(t1.Date),MONTH(t1.Date),1),Membership
The case statement will include all memberships and service types but I think this is enough for my example. Any help would be greatly appreciated! I've been on this for days.
Table 1
Table 2
You were nearly there! I've made a few changes:
SELECT
DATEFROMPARTS(YEAR(t1.Date), MONTH(t1.Date),1) AS Draft_Date,
Membership,
COUNT(CASE WHEN t1.Membership = 5 AND t1.Service_Type = 'A' THEN 1 END) as m5stA,
COUNT(CASE WHEN t1.Membership = 2 AND t1.Service_Type IN ('J','C') THEN 1 END) as m2stJC
FROM Table1 t1
GROUP BY YEAR(t1.Date), MONTH(t1.Date), Membership
Changes:
Avoid using apostrophes to alias column names, use ascii standard " double quotes if you must
When doing a conditional count, put the count outside the CASE WHEN, and have the case when return something (any non null thing will be fine - i used 1, but it could also have been 'x' etc) when the condition is met. Don't put an ELSE - CASE WHEN will return null if there is no ELSE and the condition is not met, and nulls don't COUNT (you could also write ELSE NULL, though it's redundant)
Qualify all your column names, always - this helps keep the query working when more tables are added in future, or even if new columns with the same names are added to existing tables
You forgot a THEN in the second WHEN
You don't necessarily need to GROUP BY the output of DATEFROMPARTS. When a deterministic function is used (always produces the same output from the same inputs) the db is smart enough to know that grouping on the inputs is also fine
Your example data didn't contain any data that would make the COUNT count 1+ by the way, but I'm sure you will have other conditional counts that work out (it just made it harder to test)
use sum
SELECT DATEFROMPARTS(YEAR(t1.Date),MONTH(t1.Date),1) AS Draft_Date , Membership,
sum(CASE WHEN Membership = 5 AND Service_Type = 'A' THEN 1 else 0 end),
sum(case WHEN Membership = 2 AND Service_Type IN ('J','C') then 1 else 0 end)
FROM Table1 t1 group by DATEFROMPARTS(YEAR(t1.Date),MONTH(t1.Date),1)
I have query which running fine and its doing two types of work, COUNT and SUM.
Something like
select
id,
Count (contracts) as countcontracts,
count(something1),
count(something1),
count(something1),
sum(cost) as sumCost
from
table
group by
id
My problem is: if there is no contract for a given ID, it will return 0 for COUNT and Null for SUM. I want to see null instead of 0
I was thinking about case when Count (contracts) = 0 then null else Count (contracts) end but I don't want to do it this way because I have more than 12 count positions in query and its prepossessing big amount of records so I think it may slow down query performance.
Is there any other ways to replace 0 with NULL?
Try this:
select NULLIF ( Count(something) , 0)
Here are three methods:
1. (case when count(contracts) > 0 then count(contracts) end) as countcontracts
2. sum(case when contracts is not null then 1 end) as countcontracts
3. nullif(count(contracts), 0)
All three of these require writing more complicated expressions. However, this really isn't that difficult. Just copy the line multiple times, and change the name of the variable on each one. Or, take the current query, put it into a spreadsheet and use spreadsheet functions to make the transformation. Then copy the function down. (Spreadsheets are really good code generators for repeated lines of code.)
I have these two tables (the names have been pluralized for the sake of the example):
Table Locations:
idlocation varchar(12)
name varchar(50)
Table Answers:
idlocation varchar(6)
question_number varchar(3)
answer_text1 varchar(300)
answer_text2 varchar(300)
This table can hold answers for multiple locations according a list of numbered questions that repeat on each of them.
What I am trying to do is to add up the values residing in the answer_text1 and answer_text2 columns, for each location available on the Locations table but for only an specific question and then output a value based on the result (1 or 0).
The query goes as follows using a nested table Answers to perform the SUM operation:
select
l.idlocation,
'RESULT' = (
case when (
select
sum(cast(isnull(c.answer_text1,0) as int)) +
sum(cast(isnull(c.answer_text2,0) as int))
from Answers c
where b.idlocation=c.idlocation and c.question_number='05'
) > 0 then
1
else
0
end
)
from Locations l, Answers b
where l.idlocation=b.idlocation and b.question_number='05'
In the table Answers I am saving sometimes a date string type of value for its field answer_text2 but on a different question number.
When I run the query I get the following error:
Conversion failed when converting the varchar value '27/12/2013' to data type int
I do have that value '27/12/2013' on the answer_text2 field but for a different question, so my filter gets ignored on the nested select statement after this: b.idlocation=c.idlocation, and it's adding up apparently more questions hence the error posted.
Update
According to Steve's suggested solution, I ended up implementing the filter to avoid char/varchar considerations into my SUM statement with a little variant:
Every possible not INT string value has a length greater than 2 ('00' to '99' for my question numbers) so I use this filter to determine when I am going to apply the cast.
'RESULT' =
case when (
select sum(
case when len(c.answer_text1) <= 2 then
cast(isnull(c.answer_text1,'0') as int)
else
0
end
) +
sum(
case when len(c.answer_text2) <= 2 then
cast(isnull(c.answer_text2,'0') as int)
else
0
end
)
from Answers c
where c.idlocation=b.idlocation and c.question_number='05'
) > 0
then
1
else
0
end
This is an unfortunate result of how the SQL Server query processor/optimizer works. In my opinion, the SQL standard prohibits the calculation of SELECT list expressions before the rows that will contribute to the result set have been identified, but the optimizer considers plans that violate this prohibition.
What you're observing is an error in the evaluation of a SELECT list item on a row that is not in the result set of your query. While this shouldn't happen, it does, and it's somewhat understandable, because to protect against it in every situation would exclude many efficient query plans from consideration. The vast majority of SELECT expressions will never raise an error, regardless of data.
What you can do is try to protect against this with an additional CASE expression. To protect against strings with the '/' character, for example:
... SUM(CASE WHEN c.answer_text1 IS NOT NULL and c.answer_text1 NOT LIKE '%/%' THEN CAST(c.answer_text1 as int) ELSE 0 END)...
If you're using SQL Server 2012, you have a better option: TRY_CONVERT:
...SUM(COALESCE(TRY_CONVERT(int,c.answer_text1),0)...
In your particular case, the overall database design is flawed, because numeric information should be stored in number-type columns. (This, of course, may not be your fault.) So redesign is an option, putting integer answers in integer-type columns and non-integer answer_text elsewhere. A compromise, if you can't redesign the tables, that I think will work, is to add a persisted computed column with value TRY_CONVERT(int,c.answer_text1) (or its best equivalent, based on what you know about the actual data in the table - perhaps the integer value of only columns containing no non-digit character and having length less than 9).
Your query appears correct enough, which means you have a Question 05 record with a datetime in either the answer_text1 or answer_text2 field.
Give this a shot to figure out which row has a date:
select *
from Answers
where question_number='05'
and (isdate(answer_text1) = 1 or isdate(answer_text2) = 1)
Furthermore, you could filter out any rows that have dates in them
where isdate(c.answer_text1) = 0
and isdate(c.answer_text2) = 0
and ...
Another option similar in nature to Steve's excellent answer is to filter your Answers table with a subquery like so:
select
l.idlocation,
'RESULT' = (
case when (
select
sum(cast(isnull(c.answer_text1,0) as int)) +
sum(cast(isnull(c.answer_text2,0) as int))
from (select answer_text1, answer_text2, idlocation from Answers where question_number ='05') c
where b.idlocation=c.idlocation
) > 0 then
1
else
0
end
)
from Locations l, Answers b
where l.idlocation=b.idlocation and b.question_number='05'
More generally, though, you could just have this query like this
select locations.idlocation, case when sum(case when is_numeric(answer_text1) then answer_text1 else 0 end) + sum(case when is_numeric(answer_text2) then answer_text2 else 0 end) > 0 then 1 else 0 end as RESULT from locations
inner join answers on answers.idlocation = locations.idlocation
where answers.question_number ='05'
group by locations.idlocation
Which would produce the same result.
I'm building a query with a GROUP BY clause that needs the ability to count records based only on a certain condition (e.g. count only records where a certain column value is equal to 1).
SELECT UID,
COUNT(UID) AS TotalRecords,
SUM(ContractDollars) AS ContractDollars,
(COUNTIF(MyColumn, 1) / COUNT(UID) * 100) -- Get the average of all records that are 1
FROM dbo.AD_CurrentView
GROUP BY UID
HAVING SUM(ContractDollars) >= 500000
The COUNTIF() line obviously fails since there is no native SQL function called COUNTIF, but the idea here is to determine the percentage of all rows that have the value '1' for MyColumn.
Any thoughts on how to properly implement this in a MS SQL 2005 environment?
You could use a SUM (not COUNT!) combined with a CASE statement, like this:
SELECT SUM(CASE WHEN myColumn=1 THEN 1 ELSE 0 END)
FROM AD_CurrentView
Note: in my own test NULLs were not an issue, though this can be environment dependent. You could handle nulls such as:
SELECT SUM(CASE WHEN ISNULL(myColumn,0)=1 THEN 1 ELSE 0 END)
FROM AD_CurrentView
I usually do what Josh recommended, but brainstormed and tested a slightly hokey alternative that I felt like sharing.
You can take advantage of the fact that COUNT(ColumnName) doesn't count NULLs, and use something like this:
SELECT COUNT(NULLIF(0, myColumn))
FROM AD_CurrentView
NULLIF - returns NULL if the two passed in values are the same.
Advantage: Expresses your intent to COUNT rows instead of having the SUM() notation.
Disadvantage: Not as clear how it is working ("magic" is usually bad).
I would use this syntax. It achives the same as Josh and Chris's suggestions, but with the advantage it is ANSI complient and not tied to a particular database vendor.
select count(case when myColumn = 1 then 1 else null end)
from AD_CurrentView
How about
SELECT id, COUNT(IF status=42 THEN 1 ENDIF) AS cnt
FROM table
GROUP BY table
Shorter than CASE :)
Works because COUNT() doesn't count null values, and IF/CASE return null when condition is not met and there is no ELSE.
I think it's better than using SUM().
Adding on to Josh's answer,
SELECT COUNT(CASE WHEN myColumn=1 THEN AD_CurrentView.PrimaryKeyColumn ELSE NULL END)
FROM AD_CurrentView
Worked well for me (in SQL Server 2012) without changing the 'count' to a 'sum' and the same logic is portable to other 'conditional aggregates'. E.g., summing based on a condition:
SELECT SUM(CASE WHEN myColumn=1 THEN AD_CurrentView.NumberColumn ELSE 0 END)
FROM AD_CurrentView
It's 2022 and latest SQL Server still doesn't have COUNTIF (along with regex!). Here's what I use:
-- Count if MyColumn = 42
SELECT SUM(IIF(MyColumn = 42, 1, 0))
FROM MyTable
IIF is a shortcut for CASE WHEN MyColumn = 42 THEN 1 ELSE 0 END.
Not product-specific, but the SQL standard provides
SELECT COUNT() FILTER WHERE <condition-1>,
COUNT() FILTER WHERE <condition-2>, ...
FROM ...
for this purpose. Or something that closely resembles it, I don't know off the top of my hat.
And of course vendors will prefer to stick with their proprietary solutions.
Why not like this?
SELECT count(1)
FROM AD_CurrentView
WHERE myColumn=1
I had to use COUNTIF() in my case as part of my SELECT columns AND to mimic a % of the number of times each item appeared in my results.
So I used this...
SELECT COL1, COL2, ... ETC
(1 / SELECT a.vcount
FROM (SELECT vm2.visit_id, count(*) AS vcount
FROM dbo.visitmanifests AS vm2
WHERE vm2.inactive = 0 AND vm2.visit_id = vm.Visit_ID
GROUP BY vm2.visit_id) AS a)) AS [No of Visits],
COL xyz
FROM etc etc
Of course you will need to format the result according to your display requirements.
SELECT COALESCE(IF(myColumn = 1,COUNT(DISTINCT NumberColumn),NULL),0) column1,
COALESCE(CASE WHEN myColumn = 1 THEN COUNT(DISTINCT NumberColumn) ELSE NULL END,0) AS column2
FROM AD_CurrentView