Related
Let's say we have below table of below schema.
create table result
(
id int,
task_id int,
test_name string,
test_result string
);
And dataset populated on this table looks like this.
insert into result
values (1, 1, 'test_a', 'pass'),
(2, 1, 'test_b', 'fail'),
(3, 1, 'test_c', 'pass'),
(4, 1, 'test_d', 'pass'),
(5, 2, 'test_a', 'pass'),
(6, 2, 'test_b', 'pass'),
(7, 2, 'test_c', 'pass'),
(8, 2, 'test_d', 'pass');
Basically single task has multiple test results entry. I want to retrieve task_id that has test_b fail but all the other test passed. So in this example it should return only task_id: 1.
I've tried with EXISTS and HAVING but it doesn't seem working in this case. I'm new to SQL. How can I implement it?
I would just use aggregation with a having clause:
select task_id
from result
group by task_id
having sum(case when test_name = 'test_b' and test_result = 'fail' then 1 else 0 end) = 1 and
sum(case when test_result = 'pass' then 1 else 0 end) = count(*) - 1;
The first condition validates that test_b failed. The second counts the number of passes and it should be one less then the number of rows for the task.
If your database supports except (or minus), you an use set-based operations:
select task_id
from result
where test_name = 'test_b' and test_result = 'fail'
except
select task_id
from result
where test_name <> 'test_b' and test_result = 'fail'
Maybe selecting distinct task IDs that have a fail result:
select distinct [task_id], [task_result]
from [result]
where [task_result] = 'fail'
Note that this query will scan the entire table unless there is an index on task_result.
Following code first sums test takers per task and counts fro 'test_b' whether it failed or not. Outer select ensure 'test_b' failed and other have passed.
select task_id from (
select
task_id,
count(test_result) numberoftakers,
sum(case when test_result<>'pass' AND test_name='test_b' then 1 else 0 end) numberoffailb,
sum(case when test_result='pass' then 1 else 0 end) numberofallpasses
from result
group by task_id) a
where numberoftakers=numberoffailb+numberofallpasses and numberoffailb=1
Assuming that (task_id, task_name) is a unique key of your table, you can indeed use (not) exists, along with a correlated subqueries wich ensures that other records having the same task_id did not passed.
select task_id
from result r
where
test_name = 'test_b'
and test_result = 'fail'
and not exists (
select 1
from result r1
where
r1.task_id = r.task_id
and r1.id != r.id
and r1.test_result = 'fail'
)
The left join antipattern also comes to mind:
select r.task_id
from result r
left join result r1
on r1.task_id = r.task_id
and r1.id != r.id
and r1.test_result = 'fail'
where
r.test_name = 'test_b'
and r.test_result = 'fail'
and r1.id is null
Demo on DB Fiddle - Both queries return:
| task_id |
| :------ |
| 1 |
Say I have a table:
CREATE TABLE births
(
childid INT,
momid INT,
eclampsia VARCHAR(1),
preeclampsia VARCHAR(1),
hypertension VARCHAR(1)
);
Insert records:
INSERT INTO BIRTHS (CHILDID, MOMID, ECLAMPSIA)
VALUES (654321, 123456, 'Y'),
(654321, 123456, 'Y'),
INSERT INTO BIRTHS (CHILDID, MOMID, HYPERTENSION)
VALUES (987652, 465468, 'Y'),
(987987, 465468, 'Y')
INSERT INTO BIRTHS (CHILDID, MOMID)
VALUES (687765, 465468)
INSERT INTO BIRTHS (CHILDID, MOMID, PREECLAMPSIA)
VALUES (649870, 846587, 'Y')
INSERT INTO BIRTHS (CHILDID, MOMID)
VALUES (787463, 846587);
I want to return records for all mothers who have had more than one child and have had one of these three diagnoses in more than one pregnancy.
My expected results are:
child momid eclampsia preeclampsia hypertension
-------------------------------------------------------------
654321 123456 Y
431265 123456 Y
987652 465468 Y
987987 465468 Y
How would I do write this?
I have a sloppy query that does not quite do what I want. It works to some degree, but still gives me records where the momid has had a diagnosis only for one pregnancy.
select distinct
a.*, b.eclampsia, b.preeclampsia, b.hypertension
from
births a
join
births b on a.momid = b.momid
where
a.childid != b.childid
and a.eclampsia = 'y'
and (b.eclampsia = 'y' or b.preeclampsia = 'y' or b.hypertension = 'y')
or a.preeclampsia = 'y'
and (b.preeclampsia = 'y' or b.eclampsia = 'Y' or b.hypertension = 'y')
or a.hypertension = 'y'
and (b.hypertension = 'y' or b.eclampsia = 'y' or b.preeclampsia = 'y')
order by
mapersonid
I would solve your problem with this query:
SELECT * FROM births
WHERE momid IN(
SELECT momid FROM births GROUP BY momid
HAVING COUNT(1) >1 AND
SUM(CASE WHEN eclampsia = 'Y' THEN 1 WHEN preeclampsia = 'Y' THEN 1 WHEN hypertension = 'Y' THEN 1 ELSE 0 END) > 1)
AND (eclampsia = 'Y' OR preeclampsia = 'Y' OR hypertension = 'Y')
Basicly, you filter the momids via grouping and formulate your conditions within the HAVING clause and then using this list of momids to build your desired output.
This is one way of doing it. It counts records in the births table which display one of the symptoms for each mother, using that count > 1 as a condition to display the record, as long as the record also shows one of the conditions:
SELECT childid, momid,
COALESCE(eclampsia, '') AS eclampsia,
COALESCE(preeclampsia, '') AS preeclampsia,
COALESCE(hypertension, '') AS hypertension
FROM births b1
WHERE (SELECT COUNT(*) FROM births b2 WHERE b2.momid = b1.momid AND
(ECLAMPSIA = 'Y' OR PREECLAMPSIA = 'Y' OR HYPERTENSION = 'Y')
GROUP BY momid) > 1 AND
(ECLAMPSIA = 'Y' OR PREECLAMPSIA = 'Y' OR HYPERTENSION = 'Y')
Output
child momid eclampsia preeclampsia hypertension
654321 123456 Y
431265 123456 Y
987652 465468 Y
987987 465468 Y
First get the total complications for each mom using CTE and CASEexpression , then join the CTE with Births table on Momid, then filter the moms who have more than one complication. Something like below -
;WITH BirthCTE as(
Select momid,
SUM(CASE WHEN ECLAMPSIA = 'Y' OR PREECLAMPSIA = 'Y' OR HYPERTENSION = 'Y' THEN 1 ELSE 0 END) As TotalComl
FROM births
GROUP BY momid
)
select b.* from births b
inner join BirthCTE cte on b.momid = cte.momid
Where TotalComl > 1 -- More than one complication
and (ECLAMPSIA = 'Y' OR PREECLAMPSIA = 'Y' OR HYPERTENSION = 'Y') -- atleast one complication
This is the wrong data structure. You want a table of births with no complications. Then you want a table birthComplications with one row per complication, if any.
You can restructure the data on the fly. And then aggregation:
select b.momid
from births b outer apply
(select v.complication
from (values ('eclampsia', b.eclampsia), ('hypertension', b.hypertension), ('preeclampsia', b.preeclampsia)
) v(complication, flag)
where flag = 'y'
)
group by b.momid
having count(*) > 1 and -- more than one pregnancy
count(distinct case when v.complication is not null then b.childid end) > 1;
Actually, you can simplify the logic to moms who have had complications in more than one pregnancy. This looks like:
select b.momid
from births b apply -- only keep pregnancies with complications
(select v.complication
from (values ('eclampsia', b.eclampsia), ('hypertension', b.hypertension), ('preeclampsia', b.preeclampsia)
) v(complication, flag)
where flag = 'y'
)
group by b.momid
having count(distinct b.childid) > 1;
try this
select momid, count(*) as "children",
count(eclampsia) as "eclampsia",
count(preeclampsia) as "preeclampsia",
count(hypertension) as "hypertension"
from births
group by momid
having count(*) > 1 and
(
count(eclampsia) > 1 or
count(preeclampsia) > 1 or
count(hypertension) > 1
);
you will get something like:
I need to assign two values to my select based on a CASE statement. In pseudo:
select
userid
, case
when name in ('A', 'B') then 'Apple'
when name in ('C', 'D') then 'Pear'
end as snack
from
table
;
I am assigning a value for snack. But lets say I also want to assign a value for another variable, drink based on the same conditions. One way would be to repeat the above:
select
userid
, case
when name in ('A', 'B') then 'Apple'
when name in ('C', 'D') then 'Pear'
end as snack
, case
when name in ('A', 'B') then 'Milk'
when name in ('C', 'D') then 'Cola'
end as drink
from
table
;
However, if I have to assign more values based on the same conditions, say food, drink, room, etc. this code becomes hard to maintain.
Is there a better way of doing this? Can I put this in a SQL function, like you would normally do in another (scripting) language and if so, could you please explain how?
When doing things like this I tend to use a join with a table valued constructor:
SELECT t.UserID,
s.Snack,
s.Drink
FROM Table AS T
LEFT JOIN
(VALUES
(1, 'Apple', 'Milk'),
(2, 'Pear', 'Cola')
) AS s (Condition, Snack, Drink)
ON s.Condition = CASE
WHEN t.name IN ('A', 'B') THEN 1
WHEN t.name IN ('C', 'D') THEN 2
END;
I find this to be the most flexible if I need to add further conditions, or columns.
Or more verbose, but also more flexible:
SELECT t.UserID,
s.Snack,
s.Drink
FROM Table AS T
LEFT JOIN
(VALUES
('A', 'Apple', 'Milk'),
('B', 'Apple', 'Milk'),
('C', 'Pear', 'Cola'),
('D', 'Pear', 'Cola')
) AS s (Name, Snack, Drink)
ON s.Name= t.name;
Functions destroy performance. But you could use a common-table-expression(cte):
with cte as
(
Select IsNameInList1 = case when name in ('A', 'B')
then 1 else 0 end,
IsNameInList2 = case when name in ('C', 'D')
then 1 else 0 end,
t.*
from table
)
select
userid
, case when IsNameInList1=1 then 'Apple'
when IsNameInList2=1 then 'Pear'
end as snack
, case when IsNameInList1=1 then 'Milk'
when IsNameInList2=1 then 'Cola'
end as drink
from
cte
;
On this way you have only one place to maintain.
If query performance doesn't matter and you want to use a scalar valued function like this:
CREATE FUNCTION [dbo].[IsNameInList1]
(
#name varchar(100)
)
RETURNS bit
AS
BEGIN
DECLARE #isNameInList bit
BEGIN
SET #isNameInList =
CASE WHEN #name in ('A', 'B')
THEN 1
ELSE 0
END
END
RETURN #isNameInList
END
Then you can use it in your query in this way:
select
userid
, case when dbo.IsNameInList1(name) = 1 then 'Apple'
when dbo.IsNameInList2(name) = 1 then 'Pear'
end as snack
from
table
;
But a more efficient approach would be to use a real table to store them.
Hope this will help you
SELECT userid
,(CASE flag WHEN 1 THEN 'Apple' WHEN 2 THEN 'Pear' WHEN 3 THEN '..etc' END ) as snack
,(CASE flag WHEN 1 THEN 'Milk' WHEN 2 THEN 'Cola' WHEN 3 THEN '..etc' END ) as drink
FROM (
SELECT userid
,( CASE WHEN name IN ('A', 'B') THEN 1
WHEN name IN ('C', 'D') THEN 2
WHEN name IN ('X', 'Y') THEN 3
ELSE 0 END ) AS flag
FROM table ) t
As Ganesh suggested in a comment, I recommend creating a mapping table for this and just do lookups. Much easier to interpet, maintain, and scale - all with better performance.
Imagine I am an owner of many bookstores. I keep a database of all events that occur in all of my many bookstores. Two events of note are "Book Added" and "Book Removed", for when a book is added to the inventory of a story, and when it is sold from a store. An example schema would be bookstore_id, event_name, `time.
Now say I have a second table, which maintains the current state of each bookstore, so the schema would be bookstore_id, num_books.
I want to be able to use the first table to get the count of all the "Book Added" events per bookstore, subtract the count of all the "Book Removed" events per bookstore, and then update the number of books in each bookstore in the second table.
The only way I can think to do it requires using a cursor, but I'm assuming there's a more "SQL-esque" way to do it that is more set-based and doesn't require a cursor.
You can count the events by using a GROUP BY clause.
If we would create 2 subtables where we count the added respectively the removed books, we can simply subtract the results and update these in the parent table. This will look like:
UPDATE b
SET b.numbooks = AddedBooks.BooksAdded - RemovedBooks.BooksRemoved
FROM dbo.Books b
INNER JOIN (SELECT be.book_id, count(*) AS BooksAdded
FROM dbo.BookEvents be
WHERE be.event = 'BookAdded'
GROUP BY be.book_id, be.event) AS AddedBooks
ON b.bookid = AddedBooks.book_id
INNER JOIN (SELECT be.book_id, count(*) AS BooksRemoved
FROM dbo.BookEvents be
WHERE be.event = 'BookRemoved'
GROUP BY be.book_id, be.event) AS RemovedBooks
ON b.bookid = RemovedBooks.book_id
select bookstore_id
, sum(case when event_name = "Book Removed" then -1 else 1 end) as "num books"
from bookstores
group by bookstore_id
if more than 2 events
select bookstore_id
, sum(case when event_name = "Book Removed" then -1
when event_name = "Book Added" then 1
end) as "num books"
from bookstores
group by bookstore_id
And I would just make it a view unless you come up with performance issues
We can use CTEs to get details individually and process them.
With CTE_Add AS
(
Select Bkstr_ID, Count(event_Name) As Added From temp Where event = 'Added' Group by Bkstr_ID
), CTE_Rem As
(
Select Bkstr_ID, Count(event_Name) As Removed From temp Where event = 'Removed' Group by Bkstr_ID
)
Select A.Bkstr_ID, Added - Removed
From CTE_Add A
Left Join CTE_Rem R On A.Bkstr_ID= R.Bkstr_ID
This will give you ID and count.
Instead of select, you can use Insert statement
I'd use SUM(CASE WHEN ...). Below is an example.
If object_id('tempdb..#BoookStores') Is Not Null Drop Table #BoookStores
Create Table #BoookStores (bookstore_id int, num_books int)
/* We have 3 stores */
Insert #BoookStores (bookstore_id, num_books)
Values (1, 0), (2, 0), (3, 0)
If object_id('tempdb..#Events') Is Not Null Drop Table #Events
Create Table #Events (bookstore_id int, event_name varchar(10), time dateTime Default(GetDate()) )
Insert #Events (bookstore_id, event_name)
Values
(1, 'Added'), (1, 'Added'), (1, 'Added'), (1, 'Added'), -- Added 4 books to 1. store
(2, 'Added'), (2, 'Added'), (2, 'Added'), -- Added 3 books to 2. store
(3, 'Added'), (3, 'Added'), -- Added 2 books to 3. store
/* removed 2 books from each stores */
(1, 'Removed'), (1, 'Removed'),
(2, 'Removed'), (2, 'Removed'),
(3, 'Removed'), (3, 'Removed')
/* Calculate adds and removes. Update the results */
;With Tmp As (
Select E.bookstore_id,
Sum(Case When E.event_name = 'Added' Then 1 Else 0 End) As AddCount,
Sum(Case When E.event_name = 'Removed' Then 1 Else 0 End) As RemoveCount
From #Events E
Group By E.bookstore_id
)
Update BS Set num_books = T.AddCount-T.RemoveCount
From #BoookStores BS
Inner Join Tmp T On T.bookstore_id = BS.bookstore_id
/* check results*/
Select * From #BoookStores BS
Something like this will get you in the ball park. Similar logic could be used for INSERT.
UPDATE tableA
SET tableA.num_books = tableB.num_books
FROM secondTable AS TableA
INNER JOIN (
SELECT bookstore_id,
SUM(CASE
WHEN event_name = 'Books Added'
THEN 1
END) - SUM(CASE
WHEN event_name = 'Books Removed'
THEN 1
END
) AS num_books
FROM firstTable
GROUP BY bookstore_id
) TableB ON TableA.bookstore_id = tableB.bookstore_id
You can try a query like below:
update t1
set num_books=inventory
FROM bs t1 LEFT JOIN
(select bookstore_id,SUM(case when event_name like 'A' then 1 when event_name like 'R' then -1 else NULL end) as inventory
from bse
group by bookstore_id) t2
on t1.bookstore_id=t2.bookstore_id
Live SQL demo
UPDATE bsc
SET bsc.num_books = bse.num_books
FROM bookstorecounts bsc
JOIN (SELECT bookstore_id,
SUM(CASE event_name
WHEN 'Book Removed' THEN -1
WHEN 'Book Added' THEN 1
END) AS num_books
FROM bookstoreevents
GROUP BY bookstore_id
) bse ON bsc.bookstore_id = bse.bookstore_id
I have a table which has two columns, CustomerId & Status (A, B, C).
A customer can have multiple status in different rows.
I need to get the count of different status based on following rules:
If the status of a customer is A & B, he should be counted in Status A.
If status is both B & C, it should be counted in Status B.
If status is all three, it will fall in status A.
What I need is a table with status and count.
Could please someone help?
I know that someone would ask me to write my query first, but i couldn't understand how to implement this logic in query.
You could play with different variations of this:
select customerId,
case when HasA+HasB+HasC = 3 then 'A'
when HasA+HasB = 2 then 'A'
when HasB+HasC = 2 then 'B'
when HasA+HasC = 2 then 'A'
when HasA is null and HasB is null and HasC is not null then 'C'
when HasB is null and HasC is null and HasA is not null then 'A'
when HasC is null and HasA is null and HasB is not null then 'B'
end as overallStatus
from
(
select customerId,
max(case when Status = 'A' then 1 end) HasA,
max(case when Status = 'B' then 1 end) HasB,
max(case when Status = 'C' then 1 end) HasC
from tableName
group by customerId
) as t;
I like to use Cross Apply for this type of query as it allows for use of the calculated status in the Group By clause.
Here's my solution with some sample data.
Declare #Table Table (Customerid int, Stat varchar(1))
INSERT INTO #Table (Customerid, Stat )
VALUES
(1, 'a'),
(1 , 'b'),
(2, 'b'),
(2 , 'c'),
(3, 'a'),
(3 , 'b'),
(3, 'c')
SELECT
ca.StatusGroup
, COUNT(DISTINCT Customerid) as Total
FROM
#Table t
CROSS APPLY
(VALUES
(
CASE WHEN
EXISTS
(SELECT 1 FROM #Table x where x.Customerid = t.CustomerID and x.Stat = 'a')
AND EXISTS
(SELECT 1 FROM #Table x where x.Customerid = t.CustomerID and x.Stat = 'b')
THEN 'A'
WHEN
EXISTS
(SELECT 1 FROM #Table x where x.Customerid = t.CustomerID and x.Stat = 'b')
AND EXISTS
(SELECT 1 FROM #Table x where x.Customerid = t.CustomerID and x.Stat = 'c')
THEN 'B'
ELSE t.stat
END
)
) ca (StatusGroup)
GROUP BY ca.StatusGroup
I edited this to deal with Customers who only have one status... in which case it will return A, B or C dependant on the customers status