首页 \ 问答 \ 如何在列中查询具有特定值的最新记录(How to query for the most recent records with specific values in column)

如何在列中查询具有特定值的最新记录(How to query for the most recent records with specific values in column)

我有一个DB学校(只有3个)。 在DB中,提交有关其性能的记录。

我希望用户可以选择仅查询每所学校的最新条目。

目前 - 我可以查询最新的整体...

$result = mysqli_query($con,"SELECT * FROM reports, academicyears,schools,terms
WHERE reports.report_id=(SELECT MAX(report_id) FROM reports WHERE school_id=1 OR school_id=2 OR school_id=3)
AND academicyears.ay_id=reports.ay_id
AND schools.school_id=reports.school_id
AND terms.term_id=reports.term_id
ORDER BY reports.datesubmitted DESC

但我希望能够同时找到最新的School 1&School 2&School 3。

我可以看到OR没有给我我想要的东西......它只是返回最新记录! 该查询应该是什么?

此外 - 下一步是找到最新的记录,而不必命名学校ID。 随着学校数量的增长 - 这将是完全无效的! 那可能吗?


I have a DB of schools (there are only 3). In the DB, records are submitted regarding their performance.

I want an option for the user to query only the most recent entries for each school.

At the moment - I can query the most recent overall...

$result = mysqli_query($con,"SELECT * FROM reports, academicyears,schools,terms
WHERE reports.report_id=(SELECT MAX(report_id) FROM reports WHERE school_id=1 OR school_id=2 OR school_id=3)
AND academicyears.ay_id=reports.ay_id
AND schools.school_id=reports.school_id
AND terms.term_id=reports.term_id
ORDER BY reports.datesubmitted DESC

But I would like to be able to find the most recent for School 1 & School 2 & School 3 at the same time.

I can see the OR isn't giving me what I want... it just returns the latest record! What should the query be?

Also - the next step is then find the most recent records without having to name the school ids at all. As the number of schools grow - that would be totally inefficient! Is that possible?


原文:https://stackoverflow.com/questions/30924406
更新时间:2021-08-16 15:08

最满意答案

我通过声明位置数组和数组图像以简单的方式完成了这项工作。 我有viewDidLoad方法如下。

 override func viewDidLoad() {
    super.viewDidLoad()
    self.mapView.delegate = self

    let location = [
        CLLocationCoordinate2D(latitude: 12, longitude: 77),
        CLLocationCoordinate2D(latitude: 12.5, longitude: 77.5),
        CLLocationCoordinate2D(latitude: 13, longitude: 78),
        CLLocationCoordinate2D(latitude: 13.5, longitude: 78)
    ]

    let pins = [
        "red.png",
        "blue.png",
        "green.png",
        "yellow.png"
    ]

    var annotations = [MKPointAnnotation]()
    for (index, eachLocation) in location.enumerate() {
        let pinImageName = pins[index]
        let annotation = MKPointAnnotation()
        annotation.coordinate = eachLocation
        annotation.title = "\(pinImageName)"
        annotations.append(annotation)
    }
    mapView.addAnnotations(annotations)
}

并且在viewForAnnotation委托方法中,只是从title属性获取该图像名称并显式禁用该标注

func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
    let annotationReuseId = "Truck"
    var trkPin = mapView.dequeueReusableAnnotationViewWithIdentifier(annotationReuseId)
    if trkPin == nil {
        trkPin = MKAnnotationView(annotation: annotation, reuseIdentifier: annotationReuseId)
        trkPin!.canShowCallout = false
    } else {
        trkPin!.annotation = annotation
        if let image = annotation.title {
            trkPin!.image = UIImage(named: image ?? "default.png")
        } else {
            trkPin!.image = UIImage(named: "default.png")
        }
    }
    return trkPin
}

I have done this in the simple way by declaring array of location and array images. And I have viewDidLoad method as follows.

 override func viewDidLoad() {
    super.viewDidLoad()
    self.mapView.delegate = self

    let location = [
        CLLocationCoordinate2D(latitude: 12, longitude: 77),
        CLLocationCoordinate2D(latitude: 12.5, longitude: 77.5),
        CLLocationCoordinate2D(latitude: 13, longitude: 78),
        CLLocationCoordinate2D(latitude: 13.5, longitude: 78)
    ]

    let pins = [
        "red.png",
        "blue.png",
        "green.png",
        "yellow.png"
    ]

    var annotations = [MKPointAnnotation]()
    for (index, eachLocation) in location.enumerate() {
        let pinImageName = pins[index]
        let annotation = MKPointAnnotation()
        annotation.coordinate = eachLocation
        annotation.title = "\(pinImageName)"
        annotations.append(annotation)
    }
    mapView.addAnnotations(annotations)
}

And in the viewForAnnotation delegate method just getting that image name from the title property and explicitly disabling the callout

func mapView(mapView: MKMapView, viewForAnnotation annotation: MKAnnotation) -> MKAnnotationView? {
    let annotationReuseId = "Truck"
    var trkPin = mapView.dequeueReusableAnnotationViewWithIdentifier(annotationReuseId)
    if trkPin == nil {
        trkPin = MKAnnotationView(annotation: annotation, reuseIdentifier: annotationReuseId)
        trkPin!.canShowCallout = false
    } else {
        trkPin!.annotation = annotation
        if let image = annotation.title {
            trkPin!.image = UIImage(named: image ?? "default.png")
        } else {
            trkPin!.image = UIImage(named: "default.png")
        }
    }
    return trkPin
}

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