Sometimes my eyes goes bonkers with these joins. Please help me build the select statement
product_version
id version
----------------
1 apple
2 orange
3 pineapple
executions
id class methods plat_version orig_prod_version
-----------------------------------------------------------------
1 SomeTest check 2 1
2 AnotTest submit 3 2
I want to pull from the executions but convert the numbers from the version that is in the other table. I was trying to start off and just do one at this point. Here is what I have
SELECT e.id,
e.class,
e.plat_version,
pv.id,
pv.version,
pv.version AS plat_version FROM executions e JOIN product_versions pv ON pv.version = e.plat_version
Thanks for the help.
UPDATE:
I am hoping that it pulls the records from the executions table but instead of seeing numbers for plat_version and orig_prod_version, I want to see corresponding version fields from the other table
I'm thinking something like this:
SELECT
e.id,
e.class,
pv_plat.version AS plat_version,
pv_orig.version AS orig_prod_version,
FROM executions e
JOIN product_versions pv_plat ON pv_plat.id= e.plat_version
JOIN product_versions pv_orig ON pv_orig.id= e.orig_prod_version
The idea is that you just join to the product_versions table twice, once for each id column that you have in the executions table.
SELECT *
FROM executions e
LEFT JOIN product_version v
ON e.plat_version = v.id
LEFT JOIN product_version v2
ON e.orig_prod_version = v2.id
SQL JOIN Explanation
Related
I have very limited experience with MySQL past standard queries, but when it comes to joins and relations between multiple tables I have a bit of an issue.
I've been tasked with creating a job that will pull a few values from a mysql database every 15 minutes but the info it needs to display is pulled from multiple tables.
I have worked with it for a while to figure out the relationships between everything for the phone system and I have discovered how I need to pull everything out but I'm trying to find the right way to create the job to do the joins.
I'm thinking of creating a new table for the info I need, with columns named as:
Extension | Total Talk Time | Total Calls | Outbound Calls | Inbound Calls | Missed Calls
I know that I need to start with the extension ID from my 'user' table and match it with 'extensionID' in my 'callSession'. There may be multiple instances of each extensionID but each instance creates a new 'UniqueCallID'.
The 'UniqueCallID' field then matches to 'UniqueCallID' in my 'CallSum' table. At that point, I just need to be able to say "For each 'uniqueCallID' that is associated with the same 'extensionID', get the sum of all instances in each column or a count of those instances".
Here is an example of what I need it to do:
callSession Table
UniqueCallID | extensionID |
----------------------------
A 123
B 123
C 123
callSum table
UniqueCallID | Duration | Answered |
------------------------------------
A 10 1
B 5 1
C 15 0
newReport table
Extension | Total Talk Time | Total Calls | Missed Calls
--------------------------------------------------------
123 30 3 1
Hopefully that conveys my idea properly.
If I create a table to hold these values, I need to know how I would select, join and insert those things based on that diagram but I'm unable to construct the right query/statement.
You simply JOIN the two tables, and do a group by on the extensionID. Also, add formulas to summarize and gather the info.
SELECT
`extensionID` AS `Extension`,
SUM(`Duration`) AS `Total Talk Time`,
COUNT(DISTINCT `UniqueCallID`) as `Total Calls`,
SUM(IF(`Answered` = 1,0,1)) AS `Missed Calls`
FROM `callSession` a
JOIN `callSum` b
ON a.`UniqueCallID` = b.`UniqueCallID`
GROUP BY a.`extensionID`
ORDER BY a.`extensionID`
You can use a join and group by
select
a.extensionID
, sum(b.Duration) as Total_Talk_Time
, count(b.Answered) as Total_Calls
, count(b.Answered) -sum(b.Answered) as Missed_calls
from callSession as a
inner join callSum as b on a.UniqueCallID = b.UniqueCallID
group by a.extensionID
This should do the trick. What you are being asked to do is to aggregate the number of and duration of calls. Unless explicitly requested, you do not need to create a new table to do this. The right combination of JOINs and AGGREGATEs will get the information you need. This should be pretty straightforward... the only semi-interesting part is calculating the number of missed calls, which is accomplished here using a "CASE" statement as a conditional check on whether each call was answered or not.
Pardon my syntax... My experience is with SQL Server.
SELECT CS.Extension, SUM(CA.Duration) [Total Talk Time], COUNT(CS.UniqueCallID) [Total Calls], SUM(CASE CS.Answered WHEN '0' THEN SELECT 1 ELSE SELECT 0 END CASE) [Missed Calls]
FROM callSession CS
INNER JOIN callSum CA ON CA.UniqueCallID = CS.UniqueCallID
GROUP BY CS.Extension
to display the name of all the candidates who got below 40 in exactly 2 subjects using sql
degree(degcode,name,subject)
candidate(seatno,degcode,name)
marks(seatno,dedcode,mark)
Your query can be like below-
SELECT cd.name
FROM degree dg
JOIN candidate cd ON cd.degcode=dg.degcode
JOIN marks mk ON mk.seatno=cd.seatno
WHERE mk.mark < 40
GROUP BY cd.seatno
HAVING COUNT(dg.degcode)=2;
If it does not work for you then can create a sqlfiddle with dummy data for more clairty so that I can modify query as per your requirement.
When I make this sql statement I get 6 of the same record returned. So if I expect to get 2 records returned, I get six of each record back so that is 12 in total.
SELECT
ce2.*
FROM customerentry ce, customerentrytrace cet, customerentry ce2
WHERE ce.accountid = 1
AND ce.companyid = 1
AND ce.accountid=cet.accountid
AND ce.accountid=ce2.accountid
AND ce.companyid=cet.companyid
AND ce.companyid=ce2.companyid
AND cet.documentno = '2012Faktura1'
AND cet.documenttype = 1
AND ce2.documentno = cet.offsetdocumentno
AND ce2.documenttype = cet.offsetdocumenttype
ORDER BY created;
I know that I can solve it by adding distinct, but I would like to know why I get 6 of the same record returned. Anyone who can help me?
Since we have no idea about your table structure probably there are some columns that are related 1 to n items and you haven't handled them in the WHERE section of your query.
As an extra measure you can focus on your data needs and add a GROUP BY section before your ORDER section.
You are using an INNER JOIN, so for example there are two entries in table cet matching your where clause for combining table ce and cet, giving you 2 entries/entry of table ce.
Thinking this further you can see that if there are 3 entries in table ce2 matching the where clause for combining table cet and ce2 you get 3 entries/entry of table cet.
Which makes 6 entries per entry of table ce in total, giving you 12 entries in total even if you have only 2 entries in table ce.
So think again about what join could be the right for your desired solution.
Here a link for some more explanation: Short explanation of joins
Problem might be because you have not properly joined tables. Please read about JOIN
SELECT ce2.*
FROM customerentry ce INNER JOIN customerentrytrace cet ON ce.accountid=cet.accountid AND ce.companyid=cet.companyid,
INNER JOIN customerentry ce2 ON ce.accountid=ce2.accountid AND ce.companyid=ce2.companyid AND ce2.documentno = cet.offsetdocumentno AND ce2.documenttype = cet.offsetdocumenttype
WHERE ce.accountid = 1
AND ce.companyid = 1
AND cet.documentno = '2012Faktura1'
AND cet.documenttype = 1
ORDER BY created;
I have a watchlist system that I've coded, in the overview of the users' watchlist, they would see a list of records, however the list shows duplicates when in the database it only shows the exact, correct number.
I've tried GROUP BY watch.watch_id, GROUP BY rec.record_id, none of any types of group I've tried seems to remove duplicates. I'm not sure what I'm doing wrong.
SELECT watch.watch_date,
rec.street_number,
rec.street_name,
rec.city,
rec.state,
rec.country,
usr.username
FROM
(
watchlist watch
LEFT OUTER JOIN records rec ON rec.record_id = watch.record_id
LEFT OUTER JOIN members usr ON rec.user_id = usr.user_id
)
WHERE watch.user_id = 1
GROUP BY watch.watch_id
LIMIT 0, 25
The watchlist table looks like this:
+----------+---------+-----------+------------+
| watch_id | user_id | record_id | watch_date |
+----------+---------+-----------+------------+
| 13 | 1 | 22 | 1314038274 |
| 14 | 1 | 25 | 1314038995 |
+----------+---------+-----------+------------+
GROUP BY does not "remove duplicates". GROUP BY allows for aggregation. If all you want is to combine duplicated rows, use SELECT DISTINCT.
If you need to combine rows that are duplicate in some columns, use GROUP BY but you need to to specify what to do with the other columns. You can either omit them (by not listing them in the SELECT clause) or aggregate them (using functions like SUM, MIN, and AVG). For example:
SELECT watch.watch_id, COUNT(rec.street_number), MAX(watch.watch_date)
... GROUP by watch.watch_id
EDIT
The OP asked for some clarification.
Consider the "view" -- all the data put together by the FROMs and JOINs and the WHEREs -- call that V. There are two things you might want to do.
First, you might have completely duplicate rows that you wish to combine:
a b c
- - -
1 2 3
1 2 3
3 4 5
Then simply use DISTINCT
SELECT DISTINCT * FROM V;
a b c
- - -
1 2 3
3 4 5
Or, you might have partially duplicate rows that you wish to combine:
a b c
- - -
1 2 3
1 2 6
3 4 5
Those first two rows are "the same" in some sense, but clearly different in another sense (in particular, they would not be combined by SELECT DISTINCT). You have to decide how to combine them. You could discard column c as unimportant:
SELECT DISTINCT a,b FROM V;
a b
- -
1 2
3 4
Or you could perform some kind of aggregation on them. You could add them up:
SELECT a,b, SUM(c) "tot" FROM V GROUP BY a,b;
a b tot
- - ---
1 2 9
3 4 5
You could add pick the smallest value:
SELECT a,b, MIN(c) "first" FROM V GROUP BY a,b;
a b first
- - -----
1 2 3
3 4 5
Or you could take the mean (AVG), the standard deviation (STD), and any of a bunch of other functions that take a bunch of values for c and combine them into one.
What isn't really an option is just doing nothing. If you just list the ungrouped columns, the DBMS will either throw an error (Oracle does that -- the right choice, imo) or pick one value more or less at random (MySQL). But as Dr. Peart said, "When you choose not to decide, you still have made a choice."
While SELECT DISTINCT may indeed work in your case, it's important to note why what you have is not working.
You're selecting fields that are outside of the GROUP BY. Although MySQL allows this, the exact rows it returns for the non-GROUP BY fields is undefined.
If you wanted to do this with a GROUP BY try something more like the following:
SELECT watch.watch_date,
rec.street_number,
rec.street_name,
rec.city,
rec.state,
rec.country,
usr.username
FROM
(
watchlist watch
LEFT OUTER JOIN est8_records rec ON rec.record_id = watch.record_id
LEFT OUTER JOIN est8_members usr ON rec.user_id = usr.user_id
)
WHERE watch.watch_id IN (
SELECT watch_id FROM watch WHERE user_id = 1
GROUP BY watch.watch_id)
LIMIT 0, 25
I Would never recommend using SELECT DISTINCT, it's really slow on big datasets.
Try using things like EXISTS.
You are grouping by watch.watch_id and you have two results, which have different watch IDs, so naturally they would not be grouped.
Also, from the results displayed they have different records. That looks like a perfectly valid expected results. If you are trying to only select distinct values, then you don't want ot GROUP, but you want to select by distinct values.
SELECT DISTINCT()...
If you say your watchlist table is unique, then one (or both) of the other tables either (a) has duplicates, or (b) is not unique by the key you are using.
To suppress duplicates in your results, either use DISTINCT as #Laykes says, or try
GROUP BY watch.watch_date,
rec.street_number,
rec.street_name,
rec.city,
rec.state,
rec.country,
usr.username
It sort of sounds like you expect all 3 tables to be unique by their keys, though. If that is the case, you are simply masking some other problem with your SQL by trying to retrieve distinct values.
Hello I have 2 tables:
Events (idEvent, eventName)
and
Registrations(idRegistration, idEvent, idPerson)
People register to events and I store their idPerson. Now let's say, we have 2 events (event1 and event2). I am person with id = 1 and I want to see all events and columns that will say me, if I am registered.
I mean output like :
idEvent eventName IamRegistered
1 event1 yes
2 event2 no
How can I write a query from these two tables to see similiar output?
PS: I know SQL syntax but can't figure it out, something with left join probably
You're correct, it is a left join. The CASE expression outputs Yes or No depending upon if a matching record was found.
SELECT e.idEvent, e.EventName, (CASE r.idEvent WHEN NOT NULL THEN 'Yes' ELSE 'No' END) AS IsRegistered FROM Events e
LEFT JOIN Registrations r ON r.idEvent=e.idEvent AND r.idPerson=1
It's important to have the idPerson=1 check in the JOIN clause rather than the Where clause, otherwise events that person 1 is not registred for will not be displayed.