Boucle de suppression SQL

Question

J'ai un tableau des listes de logements. Je souhaite conserver un maximum de 10 inscriptions par ville. (La plupart des villes ont moins de 10 inscriptions).

Quand je fais cette requête:

 select city, count(city) as cityCount from tREaltyTrac group by city

SQL renvoie:

Acampo  1
Acton   1
Adelanto    20
Agua Dulce  1
Aguanga 1
Akron   19
Albany  12
Albion  3
Alexandria  14
Algonac 1
Alhambra    5

Donc, Adelanto, Akron, Albany et Alexandria doivent être ramenées à 10 listes classées par le dernier champ datetime appelé "creation" (order by creation desc).

Quelqu'un peut-il penser à une procédure qui réduira les listes comme décrit?

Answer 1

NE BOUCLEZ PAS!

Je préfère marquer les rangées avec un statut, mais cela va faire comme vous voulez et les supprimer ...

essayez ceci (serveur SQL)

configurer la table

create table tREaltyTrac (city varchar(20),creation datetime)
insert into tREaltyTrac values ('Acampo'      ,getdate()) --1
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Acton'       ,getdate()) --1
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Adelanto'    ,getdate()) --20
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Agua Dulce'  ,getdate()) --1
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Aguanga'     ,getdate()) --1
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Akron'       ,getdate()) --19
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albany'      ,getdate()) --12
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albion'      ,getdate()) --3
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albion'      ,getdate()) --3
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Albion'      ,getdate()) --3
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alexandria'  ,getdate()) --14
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Algonac'     ,getdate()) --1
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alhambra'    ,getdate()) --5
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alhambra'    ,getdate()) --5
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alhambra'    ,getdate()) --5
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alhambra'    ,getdate()) --5
waitfor delay '00:00:01'
insert into tREaltyTrac values ('Alhambra'    ,getdate()) --5

afficher les valeurs du tableau

select city,count(*) from tREaltyTrac group by city
select * from tREaltyTrac

supprimez les lignes que vous ne voulez pas

delete from tREaltyTrac
    from tREaltyTrac
        inner join (select
                        city,creation, row_number() over(partition by city order by city) AS RankValue
                        from tREaltyTrac
                   ) dt on tREaltyTrac.city=dt.city AND tREaltyTrac.creation=dt.creation
    where dt. RankValue>10

montre les lignes qu'il vous reste

select * from tREaltyTrac
select city,count(*) from tREaltyTrac group by city

Answer 2

Quelque chose comme cela devrait s’occuper de vous, mais supprimer des enregistrements automatiquement n’est pas une bonne idée. Vous feriez mieux d'utiliser un drapeau actif.

DECLARE @CityName VARCHAR(30)
DECLARE CitiesOver10 CURSOR FOR select city from tREaltyTrac group by city having count(city)>10 

OPEN CitiesOver10
FETCH NEXT FROM CitiesOver10 INTO @CityName

WHILE @@FETCH_STATUS = 0
    BEGIN
        DELETE FROM 
            dbo.tREaltyTrac 
        WHERE 
            ID NOT IN (SELECT TOP 10 ID FROM dbo.tREaltyTrac WHERE city = @CityName ORDER BY Creation DESC)
            AND City = @CityName

        FETCH NEXT FROM CitiesOver10 INTO @CityName
    END

CLOSE CitiesOver10
DEALLOCATE CitiesOver10

Answer 3

vous ne devez pas supprimer les enregistrements d'une base de données. ce n'est pas parfait à 100% et je suis sûr qu'il y a de meilleures façons de le faire, mais allez-y.

declare @cities (CityName nvarchar(50), ID int identity(1,1))
declare @returns (CityName nvarchar(50), Blah nvarchar(50))
declare @cityname nvarchar(50)
declare @count int
declare @i int


insert into @cities (CityName)
select distinct CityName
from tblCities

select @count = count(*) from @cities
set @i=1

while (@i<=@count)
begin

    select @cityname = CityName from @cities where ID=@i

    select top 10 *
    from tblCities
    where CityName=@cityname
    order by Creation desc

    set @i=@i+1
end

Answer 4

Je n'ai pas le temps d'écrire le code actuel, mais que dire de quelque chose comme ça ... (en supposant que PHP)

1. Commandez votre requête initiale - ajoutez la création DESC
2. Parcourez les résultats et obtenez la date de création du 10ème résultat
3. Exécuter une autre requête qui supprime tout ce qui est inférieur à la valeur de création du 10ème résultat? - c.-à-d. SUPPRIMER O la création < $ creationDateOfTenthResult

J'espère que cela a du sens ...

Answer 5

Je choisirais les dix premiers, les jetterais dans une table temporaire, supprimerais l'original et le remplirais avec la table temporaire.

Answer 6

Dépend de votre version de SQL. Quelque chose de semblable à cela pourrait fonctionner

CHOISIR r.cité, b. *  DE tREaltyTrac r  rejoindre tREaltyTrac b sur b.Id in  (sélectionnez top 10 Id dans tREaltyTrac, où Id = r.Id commande par Id Desc)  groupe par r.City