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2019년 8월 2일 금요일

How to perform an SQLite query within an Android application?

Question


I am trying to use this query upon my Android database, but it does not return any data. Am I missing something?
SQLiteDatabase db = mDbHelper.getReadableDatabase();
    String select = "Select _id, title, title_raw from search Where(title_raw like " + "'%Smith%'" +
    ")";        
    Cursor cursor = db.query(TABLE_NAME, FROM, 
            select, null, null, null, null);
    startManagingCursor(cursor);
    return cursor;



answer


This will return you the required cursor
Cursor cursor = db.query(TABLE_NAME, new String[] {"_id", "title", "title_raw"}, 
                "title_raw like " + "'%Smith%'", null, null, null, null);


answer


Alternatively, db.rawQuery(sql, selectionArgs) exists.
Cursor c = db.rawQuery(select, null);


answer


This will also work if the pattern you want to match is a variable.
dbh = new DbHelper(this);
        SQLiteDatabase db = dbh.getWritableDatabase();
        Cursor c = db.query("TableName", new String[]{"ColumnName"}
        , "ColumnName LIKE ?" ,new String[]{_data+"%"}, null, null, null);
        while(c.moveToNext())
        {
            // your calculation goes here
        }


answer


I came here for a reminder of how to set up the query but the existing examples were hard to follow. Here is an example with more explanation.
SQLiteDatabase db = helper.getReadableDatabase();

String table = "table2";
String[] columns = {"column1", "column3"};
String selection = "column3 =?";
String[] selectionArgs = {"apple"};
String groupBy = null;
String having = null;
String orderBy = "column3 DESC";
String limit = "10";

Cursor cursor = db.query(table, columns, selection, selectionArgs, groupBy, having, orderBy, limit);
Parameters
  • table: the name of the table you want to query
  • columns: the column names that you want returned. Don't return data that you don't need.
  • selection: the row data that you want returned from the columns (This is the WHERE clause.)
  • selectionArgs: This is substituted for the ? in the selection String above.
  • groupBy and having: This groups duplicate data in a column with data having certain conditions. Any unneeded parameters can be set to null.
  • orderBy: sort the data
  • limit: limit the number of results to return


answer


Try this, this works for my code name is a String:
cursor = rdb.query(true, TABLE_PROFILE, new String[] { ID,
    REMOTEID, FIRSTNAME, LASTNAME, EMAIL, GENDER, AGE, DOB,
    ROLEID, NATIONALID, URL, IMAGEURL },                    
    LASTNAME + " like ?", new String[]{ name+"%" }, null, null, null, null);






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