Supprimer des doublons avec des mises en garde

Question

J'ai une table avec rowID, longitude, latitude, businessname, url, légende. Cela pourrait ressembler à:

rowID | long | lat | businessName | url | caption 

    1  20  -20  Pizza Hut yum.com null 

Comment puis-je supprimer tous les doublons, mais seulement garder celui qui a une URL (première priorité), ou de garder celui qui a une légende si l'autre n'a pas une URL (deuxième priorité) et supprimer le reste?

Answer 1

Voici ma technique de bouclage. Cela sera probablement rejeté pour ne pas être mainstream - et je suis cool avec ça.

DECLARE @LoopVar int 

DECLARE 
    @long int, 
    @lat int, 
    @businessname varchar(30), 
    @winner int 

SET @LoopVar = (SELECT MIN(rowID) FROM Locations) 

WHILE @LoopVar is not null 
BEGIN 
    --initialize the variables. 
    SELECT 
    @long = null, 
    @lat = null, 
    @businessname = null, 
    @winner = null 

    -- load data from the known good row. 
    SELECT 
    @long = long, 
    @lat = lat, 
    @businessname = businessname 
    FROM Locations 
    WHERE rowID = @LoopVar 

    --find the winning row with that data 
    SELECT top 1 @Winner = rowID 
    FROM Locations 
    WHERE @long = long 
    AND @lat = lat 
    AND @businessname = businessname 
    ORDER BY 
    CASE WHEN URL is not null THEN 1 ELSE 2 END, 
    CASE WHEN Caption is not null THEN 1 ELSE 2 END, 
    RowId 

    --delete any losers. 
    DELETE FROM Locations 
    WHERE @long = long 
    AND @lat = lat 
    AND @businessname = businessname 
    AND @winner != rowID 

    -- prep the next loop value. 
    SET @LoopVar = (SELECT MIN(rowID) FROM Locations WHERE @LoopVar < rowID) 
END 

Answer 2

Si possible, pouvez-vous homogénéiser, puis supprimer les doublons?

Étape 1:

UPDATE BusinessLocations 
SET BusinessLocations.url = LocationsWithUrl.url 
FROM BusinessLocations 
INNER JOIN (
    SELECT long, lat, businessName, url, caption 
    FROM BusinessLocations 
    WHERE url IS NOT NULL) LocationsWithUrl 
    ON BusinessLocations.long = LocationsWithUrl.long 
    AND BusinessLocations.lat = LocationsWithUrl.lat 
    AND BusinessLocations.businessName = LocationsWithUrl.businessName 

UPDATE BusinessLocations 
SET BusinessLocations.caption = LocationsWithCaption.caption 
FROM BusinessLocations 
INNER JOIN (
    SELECT long, lat, businessName, url, caption 
    FROM BusinessLocations 
    WHERE caption IS NOT NULL) LocationsWithCaption 
    ON BusinessLocations.long = LocationsWithCaption.long 
    AND BusinessLocations.lat = LocationsWithCaption.lat 
    AND BusinessLocations.businessName = LocationsWithCaption.businessName 

Étape 2: Supprimer les doublons.

Answer 3

solution Set-:

delete from T as t1 
where /* delete if there is a "better" row 
     with same long, lat and businessName */ 
    exists(
    select * from T as t2 where 
     t1.rowID <> t2.rowID 
     and t1.long = t2.long 
     and t1.lat = t2.lat 
     and t1.businessName = t2.businessName 
     and 
     case when t1.url is null then 0 else 4 end 
      /* 4 points for non-null url */ 
     + case when t1.businessName is null then 0 else 2 end 
      /* 2 points for non-null businessName */ 
     + case when t1.rowID > t2.rowId then 0 else 1 end 
      /* 1 point for having smaller rowId */ 
     < 
     case when t2.url is null then 0 else 4 end 
     + case when t2.businessName is null then 0 else 2 end 
     ) 

Answer 4

delete MyTable 
from MyTable 
left outer join (
     select min(rowID) as rowID, long, lat, businessName 
     from MyTable 
     where url is not null 
     group by long, lat, businessName 
    ) as HasUrl 
    on MyTable.long = HasUrl.long 
    and MyTable.lat = HasUrl.lat 
    and MyTable.businessName = HasUrl.businessName 
left outer join (
     select min(rowID) as rowID, long, lat, businessName 
     from MyTable 
     where caption is not null 
     group by long, lat, businessName 
    ) HasCaption 
    on MyTable.long = HasCaption.long 
    and MyTable.lat = HasCaption.lat 
    and MyTable.businessName = HasCaption.businessName 
left outer join (
     select min(rowID) as rowID, long, lat, businessName 
     from MyTable 
     where url is null 
      and caption is null 
     group by long, lat, businessName 
    ) HasNone 
    on MyTable.long = HasNone.long 
    and MyTable.lat = HasNone.lat 
    and MyTable.businessName = HasNone.businessName 
where MyTable.rowID <> 
     coalesce(HasUrl.rowID, HasCaption.rowID, HasNone.rowID) 

Answer 5

Cette solution vous est présenté par "des choses que j'ai appris sur Stack Overflow" la semaine dernière:

DELETE restaurant 
WHERE rowID in 
(SELECT rowID 
    FROM restaurant 
    EXCEPT 
    SELECT rowID 
    FROM (
     SELECT rowID, Rank() over (Partition BY BusinessName, lat, long ORDER BY url DESC, caption DESC) AS Rank 
     FROM restaurant 
     ) rs WHERE Rank = 1) 

Attention: Je n'ai pas testé cela sur une base de données réelle

Answer 6

Similaire à une autre réponse, mais que vous souhaitez supprimer en fonction du numéro de ligne r plus que le rang. Mélanger avec des expressions de table communes:

;WITH GroupedRows AS 
( SELECT rowID, Row_Number() OVER (Partition BY BusinessName, lat, long ORDER BY url DESC, caption DESC) rowNum 
    FROM restaurant 
) 
DELETE r 
FROM restaurant r 
JOIN GroupedRows gr ON r.rowID = gr.rowID 
WHERE gr.rowNum > 1