mysql查询显示前5个平均费率

Question

你好 假设我在mysql中有这个表：

我需要获得前5部电影评分。 我需要计算每部电影的平均速率，例如：movieID 12 =（9.5 + 9）/ 2 = 9.25（平均），然后显示前5个电影。

任何帮助？

Answer 1

var findOrSave = function(saveObj, findPrevObj, path, topKey){
    //the object used to search the collection
    var findObj = {};

    //if this is a nested schema, we need the previous schema search to match as well
    if (findPrevObj){
        for (var key in findPrevObj){
            findObj[key] = findPrevObj[key];
        }
    }

    //go through all the saveObj, compiling the findObj from string fields
    for (var key in saveObj){
        if (saveObj.hasOwnProperty(key) && typeof saveObj[key] === "string"){
            findObj[path+key] = saveObj[key]
        }
    }


    //search the DB for this record
    ThisCollection.find(findObj).exec(function(e, doc){

        //this level at least exists
        if (doc.length){

            //go through all the deeper levels in our saveObj
            for (var key in saveObj){
                var i = 0;
                    if (saveObj.hasOwnProperty(key) && typeof saveObj[key] === "string"){
                        i += 1;
                        findOrSave(saveObj[key], findObj, path+key+".", path+key);
                    }   

                    //if there were no deeper levels (basically, full record exists)        
                    if (!i){
                        lr.resume();
                    }
                }

        //this level doesn't exist, add new record or push to array
            } else {

                if (findPrevObj){

                    var toPush = {};
                    toPush[topKey] = saveObj;

                    ThisCollection.findOneAndUpdate(
                        findPrevObj,
                        {$push: toPush},
                        {safe: true, upsert: true},
                        function(err, doc) {
                            lr.resume();
                        }
                    )   
                } else {
                    // console.log("\r\rTrying to save: \r", saveObj, "\r\r\r");
                    ThisCollection.create(saveObj, function(e, doc){
                        lr.resume();
                    });
                }
            }
    });
}