Question

我想对Oracle DB中的两个表执行减号操作。第一个表是Chart_Year，其中包含trackPosition，trackArtist，trackName，previewLink。另一个表是推荐，它只跟踪艺术家，trackName，previewLink。我希望通过trackPosition对最终表进行排序。我的方式是按轨道艺术家的顺序：

SELECT trackartist, trackname, previewlink 
FROM 
    (
        SELECT 
            trackposition, trackartist, trackname, previewlink 
        FROM 
            chart_year 
        WHERE 
            chartsYear between 2004 and 2008 
        ORDER BY trackposition ASC
    )

MINUS 

SELECT 
    trackartist, trackname, previewlink 
FROM 
    recommendation 
WHERE 
    user = 'bla'

也许我可以做类似

的事情

SELECT 
    1 as trackPosition, trackartist, trackname, previewlink 
FROM 
    recommendation...

Answer 1

您可以使用MINUS：

而不是EXISTS

SELECT trackartist, trackname, previewlink
  FROM chart_year cy
 WHERE chartsYear BETWEEN 2004 AND 2008
   AND NOT EXISTS
        ( SELECT 1
            FROM recommendation r
           WHERE r.user = 'bla'
             AND r.trackartist = cy.trackartist
             AND r.trackname = cy.trackname
             AND r.previewlink = cy.previewlink
        )
 ORDER
    BY trackposition ASC
;

或LEFT OUTER JOIN：

SELECT cy.trackartist, cy.trackname, cy.previewlink
  FROM chart_year cy
  LEFT
 OUTER
  JOIN recommendation r
    ON r.user = 'bla'
   AND r.trackartist = cy.trackartist
   AND r.trackname = cy.trackname
   AND r.previewlink = cy.previewlink
 WHERE cy.chartsYear BETWEEN 2004 AND 2008
   AND r.user IS NULL -- i.e., where the join failed
 ORDER
    BY cy.trackposition ASC
;

Oracle db中的减号和订单

1 个答案: