I am using PSQL.
I have a table with a few columns, one column is event that can have 4 different values - X1, X2, Y1, Y2. I have another column that is the name of the service and I want to group by using this column.
My goal is to make a query that take an event and verify that for a specific service name I have count(X1) == count(X2) if not display a new column with "error"
Is this even possible? I am kinda new to SQL and not sure how to write this.
So far I tried something like this
select
service_name, event, count(service_name)
from
service_table st
group by
(service_name, event);
I am getting the count of each event for specific service_name but I would like to verify that count of event 1 == count of event 2 for each service_name.
I want to add that each service_name have a choice of 2 different event only.
You may not need a subquery/CTE for this, but it will work (and makes the logic easier to follow):
WITH event_counts_by_service AS (SELECT
service_name
, COUNT(CASE WHEN event='X1' THEN 1 END) AS count_x1
, COUNT(CASE WHEN event='X2' THEN 1 END) AS count_x2
FROM service_table
GROUP BY service_name)
SELECT service_name
, CASE WHEN count_x1=count_x2 THEN NULL ELSE 'Error' END AS are_counts_equal
FROM event_counts_by_service
Related
Given the following db structure:
Regions
id
name
1
EU
2
US
3
SEA
Customers:
id
name
region
1
peter
1
2
henry
1
3
john
2
There is also a PL/pgSQL function in place, defined as sendShipment() which takes (among other things) a sender and a receiver customer ID.
There is a business constraint around this which requires us to verify that both sender and receiver sit in the same region - and we need to do this as part of sendShipment(). So from within this function, we need to query the customer table for both the sender and receiver ID and verify that both their region ID is identical. We will also need to ID itself for further processing down the line.
So maybe something like this:
SELECT DISTINCT region FROM customers WHERE id IN (?, ?)
The problem with this is that the result will be either an array (if the customers are not within the same region) or a single value.
Is there are more elegant way of solving this constraint? I was thinking of SELECT INTO and use a temporary table, or I could SELECT COUNT(DISTINCT region) and then do another SELECT for the actual value if the count is less than 2, but I'd like to avoid the performance hit if possible.
There is also a PL/pgSQL function in place, defined as sendShipment() which takes (among other things) a sender and a receiver customer ID.
There is a business constraint around this which requires us to verify that both sender and receiver sit in the same region - and we need to do this as part of sendShipment(). So from within this function, we need to query the customer table for both the sender and receiver ID and verify that both their region ID is identical. We will also need to ID itself for further processing down the line.
This query should work:
WITH q AS (
SELECT
COUNT( * ) AS CountCustomers,
COUNT( DISTINCT c.Region ) AS CountDistinctRegions,
-- MIN( c.Region ) AS MinRegion
FIRST_VALUE( c.Region ) OVER ( ORDER BY c.Region ) AS MinRegion
FROM
Customers AS c
WHERE
c.CustomerId = $senderCustomerId
OR
c.CustomerId = $receiverCustomerId
)
SELECT
CASE WHEN q.CountCustomers = 2 AND q.CountDistinctRegions = 2 THEN 'OK' ELSE 'BAD' END AS "Status",
CASE WHEN q.CountDistinctRegions = 2 THEN q.MinRegion END AS SingleRegion
FROM
q
The above query will always return a single row with 2 columns: Status and SingleRegion.
SQL doesn't have a "SINGLE( col )" aggregate function (i.e. a function that is NULL unless the aggregation group has a single row), but we can abuse MIN (or MAX) with a CASE WHEN COUNT() in a CTE or derived-table as an equivalent operation.
Alternatively, windowing-functions could be used, but annoyingly they don't work in GROUP BY queries despite being so similar, argh.
Once again, this is the ISO SQL committee's fault, not PostgreSQL's.
As your Region column is UUID you cannot use it with MIN, but I understand it should work with FIRST_VALUE( c.Region ) OVER ( ORDER BY c.Region ) AS MinRegion.
As for the columns:
The Status column is either 'OK' or 'BAD' based on those business-constraints you mentioned. You might want to change it to a bit column instead of a textual one, though.
The SingleRegion column will be NOT NULL (with a valid region) if CountDistinctRegions = 2 regardless of CountCustomers, but feel free to change that, just-in-case you still want that info.
For anybody else who's interested in a simple solution, I finally came up with the (kind of obvious) way to do it:
SELECT
r.region
FROM
customers s
INNER JOIN customers r ON
s.region = r.region
WHERE s.id = 'sender_id' and r.id = 'receiver_id';
Huge credit to SELECT DISTINCT to return at most one row who helped me out a lot on this and also posted a viable solution.
I need to get a state level count on number of services. For the purposes of this I only have two services. The first column is the states, the second column is the first services and the third column is the second service. What I am struggling with is to have the second and third column show up on the results in one query. Here is my code:
SELECT Distinct allstates.Name, count (data.StateName) as CareCase_Management_Services, count(data.StateName) Caregiver_Support_Services
From
(select distinct Name from USstate) allstates
Left Join
Client2017 data
on
allstates.Name = data.StateName and
data.FiscalYear = 2017 and
data.SrvstartCareCaseMgmtCode NOT IN('999','', '998') and
data.SrvstartCaregiverSuppCode NOT IN('999','', '998')
GROUP BY allstates.Name
ORDER BY allstates.Name ASC
I understand that you are looking to compute, for each state, the count of services that match certain criteria. There are two types of services, stored in two different columns.
If so, your query could be simplified using conditional aggregation :
SELECT
allstates.Name,
SUM(CASE WHEN c.SrvstartCareCaseMgmtCode NOT IN ('999', '', '998') THEN 1 ELSE 0 END) CareCase_Management_Services,
SUM(CASE WHEN c.SrvstartCaregiverSuppCode NOT IN ('999', '', '998') THEN 1 ELSE 0 END) Caregiver_Support_Services
FROM
(SELECT DISTINCT Name FROM USstate) s
LEFT JOIN Client2017 c ON s.Name = c.StateName AND c.FiscalYear = 2017
GROUP BY allstates.Name
With this technique, each service is counted according to its own logic ; when conditions are met, the record is counted in (1 is added to the SUM()), else it is ignored (+ 0).
NB : do you really have duplicated state names in USstate ? if no, you can replace subquery (SELECT DISTINCT Name FROM USstate) s with just USstate
I have one student grade of null that I manually need to add in the below as an f (to match a grade received and reported previously). I am trying to find a way to do this in SQL Server without having to do it in Excel.
Here is what I have in the select statement for the grades portion (also showing that I am doing the group by roll up at the end):
SELECT
CASE grouping (STC_GRADE)
WHEN 1 THEN 'total' ELSE STC_GRADE
END AS 'MARK ANALYSIS'....
GROUP BY ROLLUP (STC_GRADE)...
How would I add into that select statement that if the STC_GRADE IS NULL to count it as an F so that the results show as:
'38' `F`'s
instead of '1' null and '37' F's?
To replace a NULL with a non-NULL value, you use this:
SELECT ISNULL(stc_grade, 'F') AS stc_grade
FROM your_table
Trying to do some calculations via SQL on my iSeries and have the following conundrum: I need to count the number of times a certain value appears in a column. My select statement is as follows:
Select
MOTRAN.ORDNO, MOTRAN.OPSEQ, MOROUT.WKCTR, MOTRAN.TDATE,
MOTRAN.LBTIM, MOROUT.SRLHU, MOROUT.RLHTD, MOROUT.ACODT,
MOROUT.SCODT, MOROUT.ASTDT, MOMAST.SSTDT, MOMAST.FITWH,
MOMAST.FITEM,
CONCAT(MOTRAN.ORDNO, MOTRAN.OPSEQ) As CON,
count (Concat(MOTRAN.ORDNO, MOTRAN.OPSEQ) )As CountIF,
MOROUT.SRLHU / (count (Concat(MOTRAN.ORDNO, MOTRAN.OPSEQ))) as calc
*(snip)*
With this information, I'm trying to count the number of times a value in CON appears. I will need this to do some math with so it's kinda important. My count statement doesn't work properly as it reports a certain value as occurring once when I see it appears 8 times.
Try putting a CASE statement inside a SUM().
SUM(CASE WHEN value = 'something' THEN 1 ELSE 0 END)
This will count the number of rows where value = 'something'.
Similary...
SUM(CASE WHEN t1.val = CONCAT(t2.val, t3.val) THEN 1 ELSE 0 END)
If you're on a supported version of the OS, ie 6.1 or higher...
You might be able to make use of "grouping set" functionality. Particularly the ROLLUP clause.
I can't say for sure without more understanding of your data.
Otherwise, you're going to need to so something like
wth Cnt as (select ORDNO, OPSEQ, count(*) as NbrOccur
from MOTRAN
group by ORDNO, OPSEQ
)
Select
MOTRAN.ORDNO, MOTRAN.OPSEQ, MOROUT.WKCTR, MOTRAN.TDATE,
MOTRAN.LBTIM, MOROUT.SRLHU, MOROUT.RLHTD, MOROUT.ACODT,
MOROUT.SCODT, MOROUT.ASTDT, MOMAST.SSTDT, MOMAST.FITWH,
MOMAST.FITEM,
CONCAT(MOTRAN.ORDNO, MOTRAN.OPSEQ) As CON,
Cnt.NbrOccur,
MOROUT.SRLHU / Cnt.NbrOccur as calc
from
motran join Cnt on mortran.ordno = cnt.ordno and mortran.opseq = cnt.opseq
*(snip)*
I have the following sql statement and I want to update a field on the rows returned from the select statement. Is this possible with my select? The things I have tried are not giving me the desired results:
SELECT
Flows_Flows.FlowID,
Flows_Flows.Active,
Flows_Flows.BeatID,
Flows_Flows.FlowTitle,
Flows_Flows.FlowFileName,
Flows_Flows.FlowFilePath,
Flows_Users.UserName,
Flows_Users.DisplayName,
Flows_Users.ImageName,
Flows_Flows.Created,
SUM(CASE WHEN [Like] = 1 THEN 1 ELSE 0 END) AS Likes,
SUM(CASE WHEN [Dislike] = 1 THEN 1 ELSE 0 END) AS Dislikes
FROM Flows_Flows
INNER JOIN Flows_Users ON Flows_Users.UserID = Flows_Flows.UserID
LEFT JOIN Flows_Flows_Likes_Dislikes ON
Flows_Flows.FlowID=Flows_Flows_Likes_Dislikes.FlowID
WHERE Flows_Flows.Active = '1' AND Flows_Flows.Created < DATEADD(day, -60, GETDATE())
Group By Flows_Flows.FlowID, Flows_Flows.Active, Flows_Flows.BeatID,
Flows_Flows.FlowTitle, Flows_Flows.FlowFileName, Flows_Flows.FlowFilePath,
Flows_Users.UserName, Flows_Users.DisplayName, Flows_Users.ImageName,
Flows_Flows.Created
Having SUM(CASE WHEN [Like] = 1 THEN 1 ELSE 0 END) = '0' AND SUM(CASE WHEN [Dislike] = 1
THEN 1 ELSE 0 END) >= '0'
This select statement returns exactly what I need but I want to change the Active field from 1 to 0.
yes - the general structure might be like this: (note you don't declare your primary key)
UPDATE mytable
set myCol = 1
where myPrimaryKey in (
select myPrimaryKey from mytable where interesting bits happen here )
Because you haven't made your question more clear in what result you want to achieve, I'll provide an answer with my own assumptions.
Assumption
You have a select statement that gives you stuffs, and it works as desired. What you want it to do is to make it return results and update those selected rows on the fly - basically like saying "find X, tell me about X and make it Y".
Anwser
If my assumption is correct, unfortunately I don't think there is any way you can do that. A select does not alter the table, it can only fetch information. Similarly, an update does not provide more detail than the number of rows updated.
But don't give up yet, depending on the result you want to achieve, you have alternatives.
Alternatives
If you just want to update the rows that you have selected, you can
simply write an UPDATE statement to do that, and #Randy has provided
a good example of how it will be written.
If you want to reduce calls to server, meaning you want to make just
one call to the server and get result, as well as to update the
rows, you can write store procedures to do that.
Store procedures are like functions you wrote in programming languages. It essentially defines a set of sql operations and gives them a name. Each time you call that store procedure, the set of operations gets executed with supplied inputs, if any.
So if you want to learn more about store procedures you can take a look at:
http://www.mysqltutorial.org/introduction-to-sql-stored-procedures.aspx
If I understand correctly you are looking for a syntax to be able to select the value of Active to be 0 if it is 1. The syntax for something like that is
SELECT
Active= CASE WHEN Active=1 THEN 0 ELSE Active END
FROM
<Tables>
WHERE
<JOIN Conditions>