Question

我正在查询数据库以获取输入的最近24小时内的值的光标。我可以查询并获取我想要的A_VALUE列的所有值，但我无法弄清楚如何或在何处正确编写子查询以获取A_VALUE列与where子句参数的总和并获取其值。任何想法将不胜感激。（没有编码背景，我正在学习本网站和其他网站的所有内容）

//过去24小时内获取值的当前代码是：

String[] projection = {
            DrinkContract.DrinkEntry._ID,
            DrinkContract.DrinkEntry.COLUMN_A_VALUE,
            DrinkContract.DrinkEntry.COLUMN_TIME_DATE};

    //code to query databse for last 24 hours

    String selection = DrinkContract.DrinkEntry.COLUMN_TIME_DATE + " BETWEEN strftime('%s', 'now', '-1 day') AND strftime('%s','now') ";

    Cursor dayCursor = getContentResolver().query(
            DrinkContract.DrinkEntry.CONTENT_URI,   // Provider content URI to query
            projection,             // Columns to include in the resulting Cursor
            selection,                   // selection clause
            null,
            DrinkContract.DrinkEntry.COLUMN_TIME_DATE); // Default sort order*/

    if (dayCursor == null || dayCursor.getCount() < 1) {
        return;
    }

    // Proceed with moving to the first row of the cursor and reading data from it

    while (dayCursor.moveToNext()) {

        int aValueColumnIndex = dayCursor.getColumnIndex(DrinkContract.DrinkEntry.COLUMN_A_VALUE);
        int drinkTimeDateColumnIndex = dayCursor.getColumnIndex(DrinkContract.DrinkEntry.COLUMN_TIME_DATE);

        // Extract out the value from the Cursor for the given column index
        double aValue = dayCursor.getDouble(aValueColumnIndex);


        System.out.println("The total a value is " + aValue);

Answer 1

//工作代码

 String[] projection = {
        DrinkContract.DrinkEntry._ID,
        DrinkContract.DrinkEntry.COLUMN_TIME_DATE,
            "total("+DrinkContract.DrinkEntry.COLUMN_A_VALUE+") AS totalA "};

//code to query databse for last 24 hours

String selection = DrinkContract.DrinkEntry.COLUMN_TIME_DATE + " BETWEEN strftime('%s', 'now', '-1 day') AND strftime('%s','now') ";

Cursor dayCursor = getContentResolver().query(
        DrinkContract.DrinkEntry.CONTENT_URI,   // Provider content URI to query
        projection,             // Columns to include in the resulting Cursor
        selection,                   // selection clause
        null,
        DrinkContract.DrinkEntry.COLUMN_TIME_DATE); // Default sort order*/

if (dayCursor == null || dayCursor.getCount() < 1) {
    return;
}

// Proceed with moving to the first row of the cursor and reading data from it

while (dayCursor.moveToNext()) {

   int aValueColumnIndex = dayCursor.getColumnIndex("totalA");
    int drinkTimeDateColumnIndex = dayCursor.getColumnIndex(DrinkContract.DrinkEntry.COLUMN_TIME_DATE);

    // Extract out the value from the Cursor for the given column index
    double aValue = dayCursor.getDouble(aValueColumnIndex);


    System.out.println("The total a value is " + aValue);

SQLite子查询where子句中列的总和

1 个答案: