This query for creating a list of Candidate duplicates is easy enough:
SELECT Count(*), Can_FName, Can_HPhone, Can_EMail
FROM Can
GROUP BY Can_FName, Can_HPhone, Can_EMail
HAVING Count(*) > 1
But if the actual rule I want to check against is FName and (HPhone OR Email) - how can I adjust the GROUP BY to work with this?
I'm fairly certain I'm going to end up with a UNION SELECT here (i.e. do FName, HPhone on one and FName, EMail on the other and combine the results) - but I'd love to know if anyone knows an easier way to do it.
Thank you in advance for any help.
Scott in Maine
Before I can advise anything, I need to know the answer to this question:
name phone email
John 555-00-00 john#example.com
John 555-00-01 john#example.com
John 555-00-01 john-other#example.com
What COUNT(*) you want for this data?
Update:
If you just want to know that a record has any duplicates, use this:
WITH q AS (
SELECT 1 AS id, 'John' AS name, '555-00-00' AS phone, 'john#example.com' AS email
UNION ALL
SELECT 2 AS id, 'John', '555-00-01', 'john#example.com'
UNION ALL
SELECT 3 AS id, 'John', '555-00-01', 'john-other#example.com'
UNION ALL
SELECT 4 AS id, 'James', '555-00-00', 'james#example.com'
UNION ALL
SELECT 5 AS id, 'James', '555-00-01', 'james-other#example.com'
)
SELECT *
FROM q qo
WHERE EXISTS
(
SELECT NULL
FROM q qi
WHERE qi.id <> qo.id
AND qi.name = qo.name
AND (qi.phone = qo.phone OR qi.email = qo.email)
)
It's more efficient, but doesn't tell you where the duplicate chain started.
This query select all entries along with the special field, chainid, that indicates where the duplicate chain started.
WITH q AS (
SELECT 1 AS id, 'John' AS name, '555-00-00' AS phone, 'john#example.com' AS email
UNION ALL
SELECT 2 AS id, 'John', '555-00-01', 'john#example.com'
UNION ALL
SELECT 3 AS id, 'John', '555-00-01', 'john-other#example.com'
UNION ALL
SELECT 4 AS id, 'James', '555-00-00', 'james#example.com'
UNION ALL
SELECT 5 AS id, 'James', '555-00-01', 'james-other#example.com'
),
dup AS (
SELECT id AS chainid, id, name, phone, email, 1 as d
FROM q
UNION ALL
SELECT chainid, qo.id, qo.name, qo.phone, qo.email, d + 1
FROM dup
JOIN q qo
ON qo.name = dup.name
AND (qo.phone = dup.phone OR qo.email = dup.email)
AND qo.id > dup.id
),
chains AS
(
SELECT *
FROM dup do
WHERE chainid NOT IN
(
SELECT id
FROM dup di
WHERE di.chainid < do.chainid
)
)
SELECT *
FROM chains
ORDER BY
chainid
None of these answers is correct. Quassnoi's is a decent approach, but you will notice one fatal flaw in the expressions "qo.id > dup.id" and "di.chainid < do.chainid": comparisons made by ID! This is ALWAYS bad practice because it depends on some inherent ordering in the IDs. IDs should NEVER be given any implicit meaning and should ONLY participate in equality or null testing. You can easily break Quassnoi's solution in this example by simply reordering the IDs in the data.
The essential problem is a disjunctive condition with a grouping, which leads to the possibility of two records being related through an intermediate, though they are not directly relatable.
e.g., you stated these records should all be grouped:
(1) John 555-00-00 john#example.com
(2) John 555-00-01 john#example.com
(3) John 555-00-01 john-other#example.com
You can see that #1 and #2 are relatable, as are #2 and #3, but clearly #1 and #3 are not directly relatable as a group.
This establishes that a recursive or iterative solution is the ONLY possible solution.
So, recursion is not viable since you can easily end up in a looping situation. This is what Quassnoi was trying to avoid with his ID comparisons, but in doing so he broke the algorithm. You could try limiting the levels of recursion, but you may not then complete all relations, and you will still potentially be following loops back upon yourself, leading to excessive data size and prohibitive inefficiency.
The best solution is ITERATIVE: Start a result set by tagging each ID as a unique group ID, and then spin through the result set and update it, combining IDs into the same unique group ID as they match on the disjunctive condition. Repeat the process on the updated set each time until no further updates can be made.
I will create example code for this soon.
GROUP BY doesn't support OR - it's implicitly AND and must include every non-aggregator in the select list.
I assume you also have a unique ID integer as the primary key on this table. If you don't, it's a good idea to have one, for this purpose and many others.
Find those duplicates by a self-join:
select
c1.ID
, c1.Can_FName
, c1.Can_HPhone
, c1.Can_Email
, c2.ID
, c2.Can_FName
, c2.Can_HPhone
, c2.Can_Email
from
(
select
min(ID),
Can_FName,
Can_HPhone,
Can_Email
from Can
group by
Can_FName,
Can_HPhone,
Can_Email
) c1
inner join Can c2 on c1.ID < c2.ID
where
c1.Can_FName = c2.Can_FName
and (c1.Can_HPhone = c2.Can_HPhone OR c1.Can_Email = c2.Can_Email)
order by
c1.ID
The query gives you N-1 rows for each N duplicate combinations - if you want just a count along with each unique combination, count the rows grouped by the "left" side:
select count(1) + 1,
, c1.Can_FName
, c1.Can_HPhone
, c1.Can_Email
from
(
select
min(ID),
Can_FName,
Can_HPhone,
Can_Email
from Can
group by
Can_FName,
Can_HPhone,
Can_Email
) c1
inner join Can c2 on c1.ID < c2.ID
where
c1.Can_FName = c2.Can_FName
and (c1.Can_HPhone = c2.Can_HPhone OR c1.Can_Email = c2.Can_Email)
group by
c1.Can_FName
, c1.Can_HPhone
, c1.Can_Email
Granted, this is more involved than a union - but I think it illustrates a good way of thinking about duplicates.
Project the desired transformation first from a derived table, then do the aggregation:
SELECT COUNT(*)
, CAN_FName
, Can_HPhoneOrEMail
FROM (
SELECT Can_FName
, ISNULL(Can_HPhone,'') + ISNULL(Can_EMail,'') AS Can_HPhoneOrEMail
FROM Can) AS Can_Transformed
GROUP BY Can_FName, Can_HPhoneOrEMail
HAVING Count(*) > 1
Adjust your 'OR' operation as needed in the derived table project list.
I know this answer will be criticised for the use of the temp table, but it will work anyway:
-- create temp table to give the table a unique key
create table #tmp(
ID int identity,
can_Fname varchar(200) null, -- real type and len here
can_HPhone varchar(200) null, -- real type and len here
can_Email varchar(200) null, -- real type and len here
)
-- just copy the rows where a duplicate fname exits
-- (better performance specially for a big table)
insert into #tmp
select can_fname,can_hphone,can_email
from Can
where can_fname exists in (select can_fname from Can
group by can_fname having count(*)>1)
-- select the rows that have the same fname and
-- at least the same phone or email
select can_Fname, can_Hphone, can_Email
from #tmp a where exists
(select * from #tmp b where
a.ID<>b.ID and A.can_fname = b.can_fname
and (isnull(a.can_HPhone,'')=isnull(b.can_HPhone,'')
or (isnull(a.can_email,'')=isnull(b.can_email,'') )
Try this:
SELECT Can_FName, COUNT(*)
FROM (
SELECT
rank() over(partition by Can_FName order by Can_FName,Can_HPhone) rnk_p,
rank() over(partition by Can_FName order by Can_FName,Can_EMail) rnk_m,
Can_FName
FROM Can
) X
WHERE rnk_p=1 or rnk_m =1
GROUP BY Can_FName
HAVING COUNT(*)>1
Related
I have two tables that look like the following:
Orders
------
id
tracking_number
ShippingLogs
------
tracking_number
created_at
stage
I would like to select the IDs of Orders that have ONLY ONE ShippingLog associated with it, and the stage of the ShippingLog must be error. If it has two ShippingLog entries, I don't want it. If it has one ShippingLog bug its stage is shipped, I don't want it.
This is what I have, and it doesn't work, and I know why (it finds the log with the error, but has no way of knowing if there are others). I just don't really know how to get it the way I need it.
SELECT DISTINCT
orders.id, shipping_logs.created_at, COUNT(shipping_logs.*)
FROM
orders
JOIN
shipping_logs ON orders.tracking_number = shipping_logs.tracking_number
WHERE
shipping_logs.created_at BETWEEN '2021-01-01 23:40:00'::timestamp AND '2021-01-26 23:40:00'::timestamp AND shipping_logs.stage = 'error'
GROUP BY
orders.id, shipping_logs.created_at
HAVING
COUNT(shipping_logs.*) = 1
ORDER BY
orders.id, shipping_logs.created_at DESC;
If you want to retain every column from the join of the two tables given your requirements, then I would suggest using COUNT here as an analytic function:
WITH cte AS (
SELECT o.id, sl.created_at,
COUNT(*) OVER (PARTITION BY o.id) num_logs,
COUNT(*) FILTER (WHERE sl.stage <> 'error')
OVER (PARTITION BY o.id) non_error_cnt
FROM orders o
INNER JOIN shipping_logs sl ON sl.tracking_number = o.tracking_number
WHERE sl.created_at BETWEEN '2021-01-01 23:40:00'::timestamp AND
'2021-01-26 23:40:00'::timestamp
)
SELECT id AS order_id, created_at
FROM cte
WHERE num_logs = 1 AND non_error_cnt = 0
ORDER BY id, created_at DESC;
Using ms-sql 2008 r2; am sure this is very straightforward. I am trying to identify where a unique value {ISIN} has been linked to more than 1 Identifier. An example output would be:
isin entity_id
XS0276697439 000BYT-E
XS0276697439 000BYV-E
This is actually an error and I want to look for other instances where there may be more than one entity_id linked to a unique ISIN.
This is my current working but it's obviously not correct:
select isin, entity_id from edm_security_entity_map
where isin is not null
--and isin = ('XS0276697439')
group by isin, entity_id
having COUNT(entity_id) > 1
order by isin asc
Thanks for your help.
Elliot,
I don't have a copy of SQL in front of me right now, so apologies if my syntax isn't spot on.
I'd start by finding the duplicates:
select
x.isin
,count(*)
from edm_security_entity_map as x
group by x.isin
having count(*) > 1
Then join that back to the full table to find where those duplicates come from:
;with DuplicateList as
(
select
x.isin
--,count(*) -- not used elsewhere
from edm_security_entity_map as x
group by x.isin
having count(*) > 1
)
select
map.isin
,map.entity_id
from edm_security_entity_map as map
inner join DuplicateList as dup
on dup.isin = map.isin;
HTH,
Michael
So you're saying that if isin-1 has a row for both entity-1 and entity-2 that's an error but isin-3, say, linked to entity-3 in two separe rows is OK? The ugly-but-readable solution to that is to pre-pend another CTE on the previous solution
;with UniqueValues as
(select distinct
y.isin
,y.entity_id
from edm_security_entity_map as y
)
,DuplicateList as
(
select
x.isin
--,count(*) -- not used elsewhere
from UniqueValues as x
group by x.isin
having count(*) > 1
)
select
map.isin
,map.entity_id
from edm_security_entity_map as map -- or from UniqueValues, depening on your objective.
inner join DuplicateList as dup
on dup.isin = map.isin;
There are better solutions with additional GROUP BY clauses in the final query. If this is going into production I'd be recommending that. Or if your table has a bajillion rows. If you just need to do some analysis the above should suffice, I hope.
The problem: I need to select, for each building in my table that has say at least 2 pharmacies and 2 education centers within a radius of 1km, all POIs (pharmacies, comercial centres, medical centers, education centers, police stations, fire stations) which are within 1km of the respective building. table structure->
building (id serial, name varchar )
poi_category(id serial, cname varchar) --cname being the category name of course
poi(id serial, name varchar, c_id integer)-- c_id is the FK referencing poi_category(id)
all coordinate columns are of type geometry not geography (let's call them geom)
here's the way i thought it should be done but i'm not sure it's even correct let alone the optimal solution to this problem
SELECT r.id_b, r.id_p
FROM (
SELECT b.id AS id_b, p.id AS id_p, pc.id AS id_pc,pc.cname
FROM building AS b, poi AS p, poi_category AS pc
WHERE ST_DWithin(b.geom,p.geom, 1000) AND p.c_id=pc.id
) AS r,
(
SELECT * FROM r GROUP BY id_b
) AS r1
HAVING count (
SELECT *
FROM r, r1
WHERE r1.id_b=r.id_b AND r.id_pc='pharmacy'
)>1
AND
count (
SELECT *
FROM r, r1
WHERE r1.id_b=r.id_b AND r.id_pc='ed. centre'
)>1
Is this the way to go for what i need ? What solution would be better from a performance point of view? What about the most elegant solution?
I've also posted here :http://gis.stackexchange.com/questions/11445/postgis-advanced-selection-query
This is a solution I elaborated. It's the fastest one I could find but it's still slow. Given the nature of the task I doubt it can be made faster...
WITH
building AS (
SELECT way, osm_id
FROM osm_polygon
WHERE tags #> hstore('building','yes')
--ORDER BY 1
LIMIT 1000
),
pharmacy AS (
SELECT way
FROM osm_poi
WHERE tags #> hstore('amenity','pharmacy')
),
school AS (
SELECT way
FROM osm_poi
WHERE tags #> hstore('amenity','school')
)
SELECT ST_AsText(building.way) AS geom, building.osm_id AS label
FROM building
WHERE
(SELECT count(*) > 1
FROM pharmacy
WHERE ST_DWithin(building.way,pharmacy.way,1000))
AND
(SELECT count(*) > 1
FROM school
WHERE ST_DWithin(building.way,school.way,1000))
Yours. S.
Given an example table 'Users', which has an int column named 'UserID' (and some arbitrary number of other columns), what is the best way to select all rows from which UserID appears more than once?
So far I've come up with
select * from Users where UserID in
(select UserID from Users group by UserID having COUNT(UserID) > 1)
This seems like quite an innefficient way to do this though, is there a better way?
In SQL Server 2005+ you could use this approach:
;WITH UsersNumbered AS (
SELECT
UserID,
rownum = ROW_NUMBER() OVER (PARTITION BY UserID ORDER BY UserID)
FROM Users
)
SELECT u.*
FROM Users u
INNER JOIN UsersNumbered n ON u.UserID = n.UserID AND n.rownum = 2
Provided there exists a non-clustered index on UserID, this yields a slightly worse execution plan than your approach. To make it better (actually, same as yours), you'll need to use... a subquery, however counter-intuitive it may seem:
;WITH UsersNumbered AS (
SELECT
UserID,
rownum = ROW_NUMBER() OVER (PARTITION BY UserID ORDER BY UserID)
FROM Users
)
SELECT u.*
FROM Users u
WHERE EXISTS (
SELECT *
FROM UsersNumbered n
WHERE u.UserID = n.UserID AND n.rownum = 2
);
In case of a clustered index on UserID all three solutions give the same plan.
This would do the same thing but evaluate the performance and it would likely be faster/more efficient. Of course there should be an index on this UserID column.
select u.*
from Users u
join (select UserID,count(UserID) as CUserID from Users group by UserID) u1 on u1.UserID = u.UserID
where CUserID > 1
tblUserProfile - I have a table which holds all the Profile Info (too many fields)
tblMonthlyProfiles - Another table which has just the ProfileID in it (the idea is that this table holds 2 profileids which sometimes become monthly profiles (on selection))
Now when I need to show monthly profiles, I simply do a select from this tblMonthlyProfiles and Join with tblUserProfile to get all valid info.
If there are no rows in tblMonthlyProfile, then monthly profile section is not displayed.
Now the requirement is to ALWAYS show Monthly Profiles. If there are no rows in monthlyProfiles, it should pick up 2 random profiles from tblUserProfile. If there is only one row in monthlyProfiles, it should pick up only one random row from tblUserProfile.
What is the best way to do all this in one single query ?
I thought something like this
select top 2 * from tblUserProfile P
LEFT OUTER JOIN tblMonthlyProfiles M
on M.profileid = P.profileid
ORder by NEWID()
But this always gives me 2 random rows from tblProfile. How can I solve this ?
Try something like this:
SELECT TOP 2 Field1, Field2, Field3, FinalOrder FROM
(
select top 2 Field1, Field2, Field3, FinalOrder, '1' As FinalOrder from tblUserProfile P JOIN tblMonthlyProfiles M on M.profileid = P.profileid
UNION
select top 2 Field1, Field2, Field3, FinalOrder, '2' AS FinalOrder from tblUserProfile P LEFT OUTER JOIN tblMonthlyProfiles M on M.profileid = P.profileid ORDER BY NEWID()
)
ORDER BY FinalOrder
The idea being to pick two monthly profiles (if that many exist) and then 2 random profiles (as you correctly did) and then UNION them. You'll have between 2 and 4 records at that point. Grab the top two. FinalOrder column is an easy way to make sure that you try and get the monthly's first.
If you have control of the table structure, you might save yourself some trouble by simply adding a boolean field IsMonthlyProfile to the UserProfile table. Then it's a single table query, order by IsBoolean, NewID()
In SQL 2000+ compliant syntax you could do something like:
Select ...
From (
Select TOP 2 ...
From tblUserProfile As UP
Where Not Exists( Select 1 From tblMonthlyProfile As MP1 )
Order By NewId()
) As RandomProfile
Union All
Select MP....
From tblUserProfile As UP
Join tblMonthlyProfile As MP
On MP.ProfileId = UP.ProfileId
Where ( Select Count(*) From tblMonthlyProfile As MP1 ) >= 1
Union All
Select ...
From (
Select TOP 1 ...
From tblUserProfile As UP
Where ( Select Count(*) From tblMonthlyProfile As MP1 ) = 1
Order By NewId()
) As RandomProfile
Using SQL 2005+ CTE you can do:
With
TwoRandomProfiles As
(
Select TOP 2 ..., ROW_NUMBER() OVER ( ORDER BY UP.ProfileID ) As Num
From tblUserProfile As UP
Order By NewId()
)
Select MP.Col1, ...
From tblUserProfile As UP
Join tblMonthlyProfile As MP
On MP.ProfileId = UP.ProfileId
Where ( Select Count(*) From tblMonthlyProfile As MP1 ) >= 1
Union All
Select ...
From TwoRandomProfiles
Where Not Exists( Select 1 From tblMonthlyProfile As MP1 )
Union All
Select ...
From TwoRandomProfiles
Where ( Select Count(*) From tblMonthlyProfile As MP1 ) = 1
And Num = 1
The CTE has the advantage of only querying for the random profiles once and the use of the ROW_NUMBER() column.
Obviously, in all the UNION statements the number and type of the columns must match.