In a table of my database, I have 7 records.
Now I want to update the records through a WHERE clause.
First, count the records, according to a clause
int pos = 0;
String SQL = "SELECT COUNT(posizione) FROM operatori WHERE posizione>0;";
final Cursor cur = db2.rawQuery(SQL, null);
while (cur.moveToNext()) {
pos = cur.getInt(0);
}
cur.close();
//then, with a for loop, update all the records based on a WHERE clause
for (int i = 1; i <= pos; i++) {
ContentValues cv1 = new ContentValues();
cv1.put(OperatoriTable.POSIZIONE, i);
db2.update(OperatoriTable.TABLE_NAME, cv1, OperatoriTable.POSIZIONE + ">0", null);
}
db2.close();
but, for example, if posequals 5, should enter the numbers 1,2,3,4,5. Instead, it is always inserted 1. Where am I wrong?
Your update statement probably updates multiple rows at once.
Each time you call db2.update in the for loop, it probably overwrites all rows where posizione>0 with the value currently in cv1.
Related
I have a function where I want to get the sum of values on a MySQL database table's row. This is my code:
public int getSum(int var) {
int x=0;
// Select All Query
String selectQuery = "SELECT sum(amount) FROM donations WHERE aid = '"+aid+"'";
SQLiteDatabase db = openOrCreateDatabase("shareity", Context.MODE_PRIVATE, null);
Cursor cursor = db.rawQuery(selectQuery, null);
// looping through all rows and adding to list
if (cursor.moveToFirst()) {
do {
x = cursor.getInt(0);
} while (cursor.moveToNext());
}
// return contact list
Log.d("id", "Id" + "," + x);
return x;
}
And I'm calling this in the onCreate() like this:
getSum(idk);
where idk is an integer. But my this returns 0. Can I know why please? The table's row I want to get the sum of, is also integer.
Finally figured it out. The problem was with the SQLite database. I had to use a php file to download the database from the mysql server to the local Sqlite server and then loop through it
Please check following code:
List<Database> zaznamy = new ArrayList<Database>();
String selectQuery = "SELECT X FROM Data WHERE LEVEL_1 =-24 AND LEVEL_2 =-48 AND LEVEL_3 =-55 AND LEVEL_4 =0";
File dbfile = new File("/sdcard/rtls/Databases/"+DBName );
SQLiteDatabase db = SQLiteDatabase.openOrCreateDatabase(dbfile, null);
Cursor cursor = db.rawQuery(selectQuery,null);
String bodX="empty";
if (cursor.moveToFirst())
{
do {
Database zaznam = new Database();
zaznam.setX(Integer.parseInt(cursor.getString(10)));
zaznamy.add(zaznam);
} while (cursor.moveToNext());
for (Database cn : zaznamy)
{
Log.d("X: ", Integer.toString(cn.getX()));
bodX = (cn.getX()+ "//").toString();
Log.d("X", bodX);
}
}
It says it Couldn't read row 0, col 10 from CursorWindow. I´ve tested the database with SQLite browser. Database has exactly 1 X at column 10, row 0. SQL query is working correctly I believe. Can someone tell me, why it cant be read? Or where is mistake?
EDIT:
corrected the code to:
do {
Database zaznam = new Database();
zaznam.setX(cursor.getInt(10));
zaznamy.add(zaznam);
} while (cursor.moveToNext());
because of integer value of 10th column, but still no luck. Same error
Your query has only one column in projection - column 'X'. That column has index 0 in query projection so to make your code work change your loop to looks like this:
do {
Database zaznam = new Database();
zaznam.setX(cursor.getInt(0));
zaznamy.add(zaznam);
} while (cursor.moveToNext());
To avoid that kind of problems in the future use following:
cursor.getInt(cursor.getColumnIndexOrThrow("X");
Remember that column index is related to query projection and not the sequence of columns in your database, so for example when you write "select B A C from SOME_TABLE" column B will have index 0 and column A will have index 1 etc. even if in your database they are in alphabetical order A B C.
I was having the same issue. For me. A simple work around may be:
// query database and populate an ArrayList
private void getDataFromDatabase() {
Cursor cursor = dbConnector.getSomeData();
if (cursor.getCount() > 0) {
cursor.moveToFirst();
for(int i = 0; i < cursor.getCount(); i++) {
// get column data from database and add it to ArrayList
anArrayList.add(cursor.getString(cursor.getColumnIndexOrThrow("Attr")));
cursor.moveToNext();
} // end for
} // end if
dbConnector.close();
} // end getDataFromDatabase
WHERE "Attr" is the Attribute/column name you wish to query and the anArrayList is the ArrayList you want to store the data in.
I'm creating a simple financial app where the user can input an income or expense. I cannot find anywhere how I can change the "total" amount by adding or subtracting numbers inside the database. The easiest way I can explain it is:
user enters an income of $10 : So I would add that 10 into the database.
user enters an expense of -$5 : so i would also add that into the database
the end result should be $5 as the total, but how do I do this?
I'm completely stuck as I've never use SQLite before. Thanks
You can do that simply by firing 2 commands on SQL
a) Use Select to get the value from the SQLite Database
b) In Android programming add them or subtract them
c) Update the new Total into the database
public void updateExpense(decimal Expense,String Condition) {
double current = 0;
db = this.getReadableDatabase();
String selectQuery = "select id, total from " + TABLE_YourTable ;
Cursor cursor = db.rawQuery(selectQuery, null);
int RowID=0;
if (cursor.moveToFirst()) {
current= Double.parseDouble(cursor.getString(1));
RowID= Integer.parseInt(cursor.getString(0));
}
/// Now we use condition --> if condition is positive it mean add ... if condition is negative it means
////subtract
if(Condition.equals("positive"){
current += Expense;
}else {
current =current - Expense;
}
cursor.close();
db.close();
//Your Update to SQLite
db = this.getReadableDatabase();
ContentValues values = new ContentValues();
values.put(total , current );
db.update(TABLE_YourTable , values, KEY_ID + " = ?", new String[] { String.valueOf(RowID) });
db.close();
}
I'm making an app that records the timestamp of touchscreen actions made my the user.
Then, after recording the readings in an SQLite table, I take the average of each column at the end. However, I'm getting an error:
E/AndroidRuntime(1344): java.lang.NumberFormatException: Invalid long: "1.40024e+08"
This happens when I try to take the average of each column, which I'm doing like so:
public long[] getAvg()
{
String selectQuery = "SELECT AVG(dwell_1), AVG(dwell_2), AVG(dwell_3), AVG(dwell_4), AVG(dwell_5), AVG(dwell_6), AVG(dwell_7), AVG(dwell_8), AVG(dwell_9), AVG(flight_12), AVG(flight_23), AVG(flight_34), AVG(flight_45), AVG(flight_56), AVG(flight_67), AVG(flight_78), AVG(flight_89) FROM " + TABLE;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
long[] row = new long[17];
if (cursor.moveToFirst()) {
for (int j=0; j<17; j++)
row[j] = Long.parseLong(cursor.getString(j));
}
return row;
}
It seems to be a function of the way the SQLite query displays the results. Is there any way I can circumvent/solve this? I require the precision by the way, so I can't use int or something else instead.
Oddly enough, when I run a query to just straight up display every record in the table, it works fine.
Any help will be greatly appreciated. Thanks in advance!
I believe SQLiteAVG() function returns a float value which you are trying to parse it as Long, hence the exception.
Try this :
public long[] getAvg()
{
String selectQuery = "SELECT AVG(dwell_1), AVG(dwell_2), AVG(dwell_3), AVG(dwell_4), AVG(dwell_5), AVG(dwell_6), AVG(dwell_7), AVG(dwell_8), AVG(dwell_9), AVG(flight_12), AVG(flight_23), AVG(flight_34), AVG(flight_45), AVG(flight_56), AVG(flight_67), AVG(flight_78), AVG(flight_89) FROM " + TABLE;
SQLiteDatabase db = this.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
long[] row = new long[17];
if (cursor.moveToFirst()) {
for (int j=0; j<17; j++)
row[j] = cursor.getLong(j);
}
return row;
}
SQLite returns float result, which you are trying to save to long.
Possible solutions:
Use float/double variables on Java side.
Or force SQLite to output integer/long using
SELECT CAST(avg(field) AS INTEGER) AS avg_field...
In your case, result should still fit into Java long if original was SQLite INTEGER.
Consider a simple method that fetches the average rating of an entity. The rating float value is stored between 0.0 to 5.0.
public static float getAverageReviews(SQLiteDatabase db) {
String selectQuery = "SELECT SUM(stars) * FROM " + DatabaseHelper.TABLE_STORE_REVIEWS;
Cursor c = db.rawQuery(selectQuery, null);
int count = c.getCount();
float totalSum = 0;
if(count > 0 && c.moveToFirst())
{
do {
String result = c.getString(c.getColumnIndex(StoreReviews.KEY_STARS));
totalSum += Float.parseFloat(result);
} while (c.moveToNext());
}
else {
return 0;
}
return totalSum/count;
}
I am trying to query all the columns in a table into one long text view and/or string. I know this might not be the right way to do things but I have to do this. Correct me if I am wrong, I was under the impression that move next would get the next column in the row:
Cursor c = db.get();
if(c.moveToFirst){
do{
string = c.getString(0);
}while(c.moveToNext);
}
I thought that this would get the first column and display all of its contents instead I get the first column and first row. What am I doing wrong? Is there a better or real way to get this information without using a ListView?
The simple use is:
Cursor cursor = db.query(...);
while (cursor.moveToNext()) {
...
}
moveToFirst is used when you need to start iterating from start after you have already reached some position.
Avoid using cursor.getCount() except if it is required.
And never use a loop over getCount().
getCount is expensive - it iterates over many records to count them. It doesn't return a stored variable. There may be some caching on a second call, but the first call doesn't know the answer until it is counted.
If your query matches 1000 rows, the cursor actually has only the first row. Each moveToNext searches and finds the next match. getCount must find all 1000. Why iterate over all if you only need 10? Why iterate twice?
Also, if your query doesn't use an index, getCount may be even slower - getCount may go over 10000 records even though the query matches only 100. Why loop 20000 instead of 10000?
For clarity a complete example would be as follows which I trust is of interest. As code comments indicated we essentially iterate over database rows and then columns to form a table of data as per database.
Cursor cursor = getActivity().getContentResolver().query(uri, projection, null, null,
null);
//if the cursor isnt null we will essentially iterate over rows and then columns
//to form a table of data as per database.
if (cursor != null) {
//more to the first row
cursor.moveToFirst();
//iterate over rows
for (int i = 0; i < cursor.getCount(); i++) {
//iterate over the columns
for(int j = 0; j < cursor.getColumnNames().length; j++){
//append the column value to the string builder and delimit by a pipe symbol
stringBuilder.append(cursor.getString(j) + "|");
}
//add a new line carriage return
stringBuilder.append("\n");
//move to the next row
cursor.moveToNext();
}
//close the cursor
cursor.close();
}
I am coding my loops over the cusror like this:
cursor.moveToFirst();
while(!cursor.isAfterLast()) {
cursor.getString(cursor.getColumnIndex("column_name"));
cursor.moveToNext();
}
That always works. This will retrieve the values of column "column_name" of all rows.
Your mistake is that you loop over the rows and not the columns.
To loop over the columns:
cursor.moveToFirst();
for(int i = 0; i < cursor.getColumnNames().length; i++){
cursor.getString(i);
}
That will loop over the columns of the first row and retrieve each columns value.
moveToNext move the cursor to the next row. and c.getString(0) will always give you the first column if there is one. I think you should do something similar to this inside your loop
int index = c.getColumnIndex("Column_Name");
string = c.getString(index);
cursor.moveToFirst() moves the cursor to the first row. If you know that you have 6 columns, and you want one string containing all the columns, try the following.
c.moveToFirst();
StringBuilder stringBuilder = new StringBuilder();
for(int i = 0; i < 6; i++){
stringBuilder.append(c.getString(i));
}
// to return the string, you would do stringBuilder.toString();