I have a database Library, which has a lot of tables and we need 3 tables for query:
Table Librarians: ID, Surname;
Table StudentCard: ID, foreign key on table Librarians and other columns which we don't use
Table TeacherCard: ID, foreign key on table Librarians and other columns which we don't use
Query: select the librarian's surname, which gave the most count of books.
I know, how to resolve, when I took data only from one table, e. g. TeacherCard
SELECT TOP 1 WITH TIES
Librarians.LastName, MAX(Librarians.CountOfBooks) AS Books
FROM
(SELECT
L.LastName, COUNT(*) AS CountOfBooks
FROM Libs L, T_Cards T
WHERE T.Id_Lib IN (SELECT L.Id)
GROUP BY L.LastName) AS Librarians
GROUP BY
Librarians.LastName
ORDER BY
MAX(Librarians.CountOfBooks) DESC
GO
I don't know, how to use data from TeacherCard and from StudetnCard at the same time.
Please, help to write this query.
I have a right resolving !!!!
SELECT TOP 1 B.Name, B.CountOut
FROM
(SELECT A.Name, SUM(A.Count) AS CountOut
FROM
(SELECT Libs.LastName AS Name, COUNT(S_Cards.DateOut) AS [Count]
FROM Libs JOIN S_Cards ON S_Cards.Id_Lib = Libs.Id
GROUP BY Libs.LastName
UNION ALL
SELECT Libs.LastName AS Name, COUNT(T_Cards.DateOut) AS [Count]
FROM Libs JOIN T_Cards ON T_Cards.Id_Lib = Libs.Id
GROUP BY Libs.LastName) AS A
GROUP BY A.Name ) AS B
ORDER BY B.CountOut DESC
I have another right answer:
SELECT TOP 2 LastName, COUNT (*) [count] FROM
(SELECT LastName FROM Libs L, S_Cards S
WHERE S.id_lib = L.id
UNION ALL
SELECT LastName FROM Libs L, T_Cards T
WHERE T.id_lib = L.id) As Res
GROUP By LastName
ORDER BY COUNT (*) DESC
Related
I have a table that Tracks Employees and the days they have spent in a policy. I don't generate this Data, it is dumped to our Server Daily.
The table looks like this:
My Goal is to get rid of the duplicates by keeping only the most recent Date.
In this example, if I run the query, I would like it to keep Rows 11 for Nicholas Morris and 14 for Tiana Sullivan.
Assumption: First name and Last Name combo are unique
So far,
This is what I have been doing:
select *
from
Employees IN(
Select ID
from Employees
group by FirstName, lastName
Having count(*) > 1)
This returns to me the rows that have duplicates and I have to manually search them and remove the ones I don't want to keep.
I am sure there is a better way of doing this
Thanks for your help
You can use a CTE and ROW_NUMBER() function to do it.
The query to get the data is:
SELECT ID, FirstName, LastName, ROW_NUMBER()
OVER (PARTITION BY FirstName, LastName ORDER BY DaysInPolicy DESC) AS Identifier
FROM
Employees
The query to remove duplicates is:
;WITH CTE AS (
SELECT ID, ROW_NUMBER()
OVER (PARTITION BY FirstName, LastName ORDER BY DaysInPolicy DESC) AS Identifier
FROM
Employees
)
DELETE E
FROM
Employees E
INNER JOIN CTE C ON C.ID = E.ID
WHERE
C.Identifier > 1
You could delete using an exists operator where you remove any row that has the same first and last name, but with a newer date:
DELETE FROM employees e1
WHERE EXISTS (SELECT *
FROM employees e2
WHERE e1.FirstName = e2.FirstName AND
e1.LastName = e2.LastName AND
e1.DaysInPolicy < e2.DaysInPolicy)
Try this:
SELECT * FROM
(
SELECT *, ROW_NUMBER() OVER (PARTITION BY Last_Name, First_Nmae ORDER BY DaysInPolicy DESC) AS RowNum
FROM Employees
) AS Emp
WHERE Emp.RowNum > 1
I have 36 Sales tables each referred to one store:
st1.dbo.Sales
st2.dbo.Sales
...
st35.dbo.Sales
st36.dbo.Sales
Each record has the following key columns:
UserName, PostalCode, Location, Country, InvoiceAmount, ItemsCount, StoreID
Here is SQLFiddle
I need to copy into Customers table all Username (and their details) that are not already present into Customers
in case of duplicated it is required to use the fields of record where InvoiceAmount is MAX
I tried to build a query but looks too complicated and it is also wrong because in CROSS APPLY should consider the full list of Sales Tables
INSERT INTO Customers (.....)
SELECT distinct
d.UserName,
w.postalCode,
w.location,
W.country,
max(w.invoiceamount) invoiceamount,
max(w.itemscount) itemscount,
w.storeID
FROM
(SELECT * FROM st1.dbo.Sales
UNION
SELECT * FROM st2.dbo.Sales
UNION
...
SELECT * FROM st36.dbo.Sales) d
LEFT JOIN
G.dbo.Customers s ON d.Username = s.UserName
CROSS APPLY
(SELECT TOP (1) *
FROM s.dbo.[Sales]
WHERE d.Username=w.Username
ORDER BY InvoiceAmount DESC) w
WHERE
s.UserName IS NULL
AND d.username IS NOT NULL
GROUP BY
d.UserName, w.postalCode, w.location,
w.country, w.storeID
Can somebody please give some hints?
As a basic SQL query, I'd create a row_number in the inner subquery and then join to customers and then isolated the max invoice number for each customer not in the customer table.
INSERT INTO Customers (.....)
SELECT w.UserName,
w.postalCode,
w.location,
w.country,
w.invoiceamount,
w.itemscount,
w.storeID
FROM (select d.*,
row_number() over(partition by d.Username order by d.invoiceamount desc) rownumber
from (SELECT *
FROM st1.dbo.Sales
UNION
SELECT *
FROM st2.dbo.Sales
UNION
...
SELECT *
FROM st36.dbo.Sales
) d
LEFT JOIN G.dbo.Customers s
ON d.Username = s.UserName
WHERE s.UserName IS NULL
AND d.username IS NOT NULL
) w
where w.rownumber = 1
Using your fiddle this will select distinct usernames rows with max invoiceamount
with d as(
SELECT * FROM Sales
UNION
SELECT * FROM Sales2
)
select *
from ( select *,
rn = row_number() over(partition by Username order by invoiceamount desc)
from d) dd
where rn=1;
step 1 - use cte .
select username , invoiceamount ,itemscount from Sales
UNION all
select user name , invoiceamount ,itemscount from Sales
.....
...
step 2
next cte use group by and get max invoiceamount ,itemscount for user of last result set.
,cte2 as (
select user name , max (invoiceamount) as invoiceamount ,max(itemscount) as itemscount from cte)
step3
use left join with user table and find missing record and itemscount invoiceamount
I have a table with 500,000+ records, and fields for ID, first name, last name, and email address. What I'm trying to do is find rows where the first name AND last name are both duplicates (as in the same person has two separate IDs, email addresses, or whatever, they're in the table more than once). I think I know how to find the duplicates using GROUP BY, this is what I have:
SELECT first_name, last_name, COUNT(*)
FROM person_table
GROUP BY first_name, last_name
HAVING COUNT(*) > 1
The problem is that I need to then move the entire row with these duplicated names into a different table. Is there a way to find the duplicates and get the whole row? Or at least to get the IDs as well? I tried using a self-join, but got back more rows than were in the table to begin with. Would that be a better approach? Any help would be greatly appreciated.
The most effective way to remove duplicate rows is with a self-join:
DELETE FROM person_table a
WHERE a.rowid >
ANY (SELECT b.rowid
FROM person_table b
WHERE a.first_name = b.first_name
AND a.last_name = b.last_name);
This will remove all duplicates even if there are more than one duplicate row.
There is more on removing duplicates and differing methods here: http://www.dba-oracle.com/t_delete_duplicate_table_rows.htm
Hope it helps...
EDIT: As per your comments, if you want to select all but one of the duplicates then
SELECT *
FROM person_table a
WHERE a.rowid >
ANY (SELECT b.rowid
FROM person_table b
WHERE a.first_name = b.first_name
AND a.last_name = b.last_name);
An index on (first_name, last_name) or on (last_name, first_name) would help:
SELECT t.*
FROM
person_table t
JOIN
( SELECT first_name, last_name
FROM person_table
GROUP BY first_name, last_name
HAVING COUNT(*) > 1
) dup
ON dup.last_name = t.last_name
AND dup.first_name = t.first_name
or:
SELECT t.*
FROM person_table t
WHERE EXISTS
( SELECT *
FROM person_table dup
WHERE dup.last_name = t.last_name
AND dup.first_name = t.first_name
AND dup.ID <> t.ID
)
This will give you an ID you want to move/delete/etc. Note that it does not work if count(*) > 2, as you get only 1 ID (you could re-run your query for these cases).
SELECT max(ID), first_name, last_name, COUNT(*)
FROM person_table
GROUP BY first_name, last_name
HAVING COUNT(*) > 1
Edit: You can use COLLECT to get all IDs at once (but be careful, as you only want to move/delete all but one)
To add another option, I usually use this one to remove duplicates:
delete from person_table
where rowid in (select rid
from (select rowid rid, row_number() over
(partition by first_name,last_name order by rowid) rn
from person_table
)
where rn <> 1 )
select first(orderid), accountid
from [Order]
group by AccountId
order by DateCreated desc
first() is invalid function.
max() does not work for unique identifiers
How would I get the last orderid created for all accounts? Thanks.
Something like (untested):
;WITH CTE_LatestOrders AS (
select accountid, lastcreated = max(datecreated)
from [Order]
group by accountid
)
select
accountid, orderid
from
[Orders] o
join CTE_LatestOrders l
on o.AccountID = l.AccountID
and o.datecreated = l.lastcreated
Max() does work for unique identifiers as of MS SQL 2012
You can proceed with below as well.
Select Temp.orderid, T.AccountId, T.DateCreated
From
(
Select AccountId, max(DateCreated) as DateCreated
From [Order]
Group By AccountId
)T
Inner Join [Order] Temp on Temp.AccountId = T.AccountId
AND Temp.DateCreated = T.DateCreated
A CTE is not a UDT/temp table; think of a CTE as a view that is defined only for your current query. Just like a view, a CTE is expanded and folded into the overall query plan. Global optimization will still occur, but do not think that just because you use a CTE you will only execute the query once. Here is a trivial example that fits in this space: WITH vw AS ( SELECT COUNT(*) c FROM Person ) SELECT a.c, b.c FROM vw a, vw b; The query plan will clearly show two scans/aggregations and a join instead of just projecting the same result twice.
I have two columns:
namecode name
050125 chris
050125 tof
050125 tof
050130 chris
050131 tof
I want to group by namecode, and return only the name with the most number of occurrences. In this instance, the result would be
050125 tof
050130 chris
050131 tof
This is with SQL Server 2000
I usually use ROW_NUMBER() to achieve this. Not sure how it performs against various data sets, but we haven't had any performance issues as a result of using ROW_NUMBER.
The PARTITION BY clause specifies which value to "group" the row numbers by, and the ORDER BY clause specifies how the records within each "group" should be sorted. So partition the data set by NameCode, and get all records with a Row Number of 1 (that is, the first record in each partition, ordered by the ORDER BY clause).
SELECT
i.NameCode,
i.Name
FROM
(
SELECT
RowNumber = ROW_NUMBER() OVER (PARTITION BY t.NameCode ORDER BY t.Name),
t.NameCode,
t.Name
FROM
MyTable t
) i
WHERE
i.RowNumber = 1;
select distinct namecode
, (
select top 1 name from
(
select namecode, name, count(*)
from myTable i
where i.namecode = o.namecode
group by namecode, name
order by count(*) desc
) x
) as name
from myTable o
SELECT max_table.namecode, count_table2.name
FROM
(SELECT namecode, MAX(count_name) AS max_count
FROM
(SELECT namecode, name, COUNT(name) AS count_name
FROM mytable
GROUP BY namecode, name) AS count_table1
GROUP BY namecode) AS max_table
INNER JOIN
(SELECT namecode, COUNT(name) AS count_name, name
FROM mytable
GROUP BY namecode, name) count_table2
ON max_table.namecode = count_table2.namecode AND
count_table2.count_name = max_table.max_count
I did not try but this should work,
select top 1 t2.* from (
select namecode, count(*) count from temp
group by namecode) t1 join temp t2 on t1.namecode = t2.namecode
order by t1.count desc
Here are to examples that you could use but the temp table use is more efficient than the view, but was done on a small data sample. You would want to check your own statistics.
--Creating A View
GO
CREATE VIEW StateStoreSales AS
SELECT t.state,t.stor_id,t.stor_name,SUM(s.qty) 'TotalSales'
,ROW_NUMBER() OVER (PARTITION BY t.state ORDER BY SUM(s.qty) DESC) AS 'Rank'
FROM [dbo].[sales] s
JOIN [dbo].[stores] t ON (s.stor_id = t.stor_id)
GROUP BY t.state,t.stor_id,t.stor_name
GO
SELECT * FROM StateStoreSales
WHERE Rank <= 1
ORDER BY TotalSales Desc
DROP VIEW StateStoreSales
---Using a Temp Table
SELECT t.state,t.stor_id,t.stor_name,SUM(s.qty) 'TotalSales'
,ROW_NUMBER() OVER (PARTITION BY t.state ORDER BY SUM(s.qty) DESC) AS 'Rank' INTO #TEMP
FROM [dbo].[sales] s
JOIN [dbo].[stores] t ON (s.stor_id = t.stor_id)
GROUP BY t.state,t.stor_id,t.stor_name
SELECT * FROM #TEMP
WHERE Rank <= 1
ORDER BY TotalSales Desc
DROP TABLE #TEMP