Android SQL Query syntax

Question

I use this java class to create a database:

public class DBhelper extends SQLiteOpenHelper {

private static final String DB_NAME = "grades.db";
private static final int DB_VERSION = 1;
public static final String TABELLA_RICETTE = "TabellaRicette";
public static final String COL_ID="ColonnaId";
public static final String COL_NOME="ColonnaNome";
public static final String COL_TIPO = "ColonnaTipo";
public static final String COL_IMMAGINE = "ColonnaImmagine";
public static final String COL_ATTRIBUTI="ColonnaAttributi";
public static final String COL_INGREDIENTI = "ColonnaIngredienti";
public static final String COL_DIFFICOLTA="ColonnaDifficolta";
public static final String COL_DESCRIZIONE="ColonnaDescrizione";

public DBhelper(Context context){
    super(context, DB_NAME, null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    String sql_tab = "create table " + TABELLA_RICETTE + "( " +
            COL_ID + " integer primary key autoincrement, " +
            COL_NOME + " text not null, " +
            COL_TIPO + " text not null, " +
            COL_IMMAGINE + " text not null, " +
            COL_ATTRIBUTI + " text not null, " +
            COL_INGREDIENTI + " text not null, " +
            COL_DIFFICOLTA + " text not null, " +
            COL_DESCRIZIONE + " text not null " +
            ");";
    db.execSQL(sql_tab);
}

@Override
   public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
}

I use this function to obtain all the information in the database:

public Cursor get_all() {
    return getWritableDatabase().query(TABELLA_RICETTE, null, null, null, null, null, null);
}

Now i would make a more specific query, selecting all the element that has a particular String s1 in COL_TIPO and String s2 in COL_DIFFICOLTA.

I tried to write something, but maybe i am wrong in syntax too.

Can you help me with this function?

public Cursor get_something(String s1,String s2) {
   String whereClause="COL_TIPO=? AND COL_DIFFICOLTA=?";
   String[] whereArgs=new String[] {s1,s2};
   return getWritableDatabase().query(TABELLA_RICETTE,null,null,whereClause,whereArgs,null,null,null);
}

So what exactly is the problem here?

Marc B
– Marc B

2016-06-16 15:55:59 +00:00
Commented Jun 16, 2016 at 15:55 — Marc B
– Marc B, Commented Jun 16, 2016 at 15:55

CL. · Accepted Answer · 2016-06-16 15:56:05Z

1

COL_TIPO is not the name of a column but the name of the symbol that contains the name of the column.

You have to put the symbols' values into the SQL string:

String whereClause = COL_TIPO+"=? AND "+COL_DIFFICOLTA+"=?";

answered Jun 16, 2016 at 15:56

CL.

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