How to add a value of a variable in a sqlite database existing column?

Question

I would like to ask for some help with my android code. I am trying to develop a quiz app using SQLite.My Database has two Tables. One for Students Information and one for the Questions and answers. Students Information such as Name, Student ID e.c. are inputs through textViews . After taking the Quiz in the Result activity the Score shown up. But i also want this score to be kept in a column COLUMN_SCORE of Student_trable.

I tried to update the table using this method:

 `public static void addScore (int StudentScore){

    ContentValues cv = new ContentValues();
    cv.put(DataContract.StudentTable.COLUMN_SCORE, StudentScore);

    Cursor c = db.rawQuery("SELECT * FROM student_info ORDER BY id DESC LIMIT 1 " ,null);

    db.update(DataContract.StudentTable.TABLE_NAME1, cv, DataContract.StudentTable.COLUMN_SCORE +  "= ?", new String[] {String.valueOf (c)});
    db.close();`

but i failed. Any suggestion please? Here is some more details of my code:

forpas · Accepted Answer · 2022-01-10 20:25:25Z

1

You can use a subquery in the WHERE clause argument of the update() method, so that there is no need for a SELECT query to retrieve the last id:

public static void addScore(int studentScore) {
    String table = DataContract.StudentTable.TABLE_NAME1;
    String id = DataContract.StudentTable.COLUMN_ID;

    ContentValues cv = new ContentValues();
    cv.put(DataContract.StudentTable.COLUMN_SCORE, studentScore);
    db.update(
        table, 
        cv, 
        id + " = (SELECT MAX(" + id + ") FROM " + table + ")", 
        null
    );
    db.close();
}

edited Jan 10, 2022 at 20:25

answered Jan 10, 2022 at 13:16

forpas

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9 Comments

fotonio Over a year ago

Good point but i can't use id as an argument in method addScore in the Class from where i call the method...It's too complicated. I have to call id inside addscore. Thats why i thought that i could pick it from the table internally...

forpas Over a year ago

@fotonio one way or another you have to use the id. What makes no sense is the SELECT query.

fotonio Over a year ago

I was trying to find a way to pick the last id of the table ..

forpas Over a year ago

@fotonio why the last id?

fotonio Over a year ago

Because the last player dont know his position at the table so he has an unknown id

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