Develop Reference

Sql Query to retrieve a particular data from particular column and row in android?

I want to fetch phone number linked to particular email in the database. I am not able to find the query for it or how
public String getContactNumber(String email){
SQLiteDatabase db = this.getReadableDatabase();
String query = "SELECT " + COLUMN_USER_MOBILE_NUMBER + " FROM " + TABLE_USER + " WHERE " + email + " = " + COLUMN_USER_EMAIL;
Cursor cursor = db.rawQuery(query,null);
//What to put here to extract the data.
String contact = cursor.getString(get);
cursor.close();
return contact;
}
to extract the data. Completely a beginner

Try this ..
public List<String> getMyItemsD(String emailData) {
List<String> stringList = new ArrayList<>();
SQLiteDatabase db = this.getReadableDatabase();
String selectQuery = "SELECT COLUMN_USER_MOBILE_NUMBER FROM " + USER_TABLE_NAME + " WHERE email= " + emailData;
Cursor c = db.rawQuery(selectQuery, null);
if (c != null) {
c.moveToFirst();
while (c.isAfterLast() == false) {
String name = (c.getString(c.getColumnIndex("Item_Name")));
stringList.add(name);
c.moveToNext();
}
}
return stringList;
}

public String getContactNumber(String email){
String contact = "";
SQLiteDatabase db = this.getReadableDatabase();
String query = "SELECT " + COLUMN_USER_MOBILE_NUMBER + " FROM " + TABLE_USER + " WHERE " + email + " = " + COLUMN_USER_EMAIL;
Cursor cursor = db.rawQuery(query,null);
if(cursor.getCount()>0) {
cursor.moveToNext();
contact = cursor.getString(cursor.getColumnIndex(COLUMN_USER_MOBILE_NUMBER));
}
//What to put here to extract the data.
cursor.close();
return contact;
}
From this method you get phone number value of that email which you pass any other method easily.

I'd suggest the following :-
public String getContactNumber(String email){
String contact = "NO CONTACT FOUND"; //<<<<<<<<<< Default in case no row is found.
SQLiteDatabase db = this.getWritableDatabase(); //<<<<<<<<<< Generally getReadable gets a writable database
String[] columns_to_get = new String[]{COLUMN_USER_MOBILE_NUMBER};
String whereclause = COLUMN_USER_EMAIL + "=?";
String[] whereargs = new String[]{email};
Cursor cursor = db.query(TABLE_USER,columns_to_get,whereclause,whereargs,null,null,null);
//What to put here to extract the data.
if (cursor.moveToFirst()) {
contact = csr.getString(csr.getColumnIndex(COLUMN_USER_MOBILE_NUMBER));
}
cursor.close();
return contact;
}
The above does assumes that there will only be 1 row per email (which is most likely).
Explanations
A default value is set so that you can easily tell if an invalid/non-existent email is passed (you'd check the return value if need be (might be easier to simply have "" and check the length as a check)).
getReadableDatabase has been replaced with getWritableDatabase as unless there are issues with the database a writable database will be returned, as per :-
Create and/or open a database. This will be the same object returned
by getWritableDatabase() unless some problem, such as a full disk,
requires the database to be opened read-only. In that case, a
read-only database object will be returned. If the problem is fixed, a
future call to getWritableDatabase() may succeed, in which case the
read-only database object will be closed and the read/write object
will be returned in the future.
getReadableDatabase
Note no real problem either way;
The recommended query method has been used instead of the rawQuery method. This has distinct advantages, it builds the underlying SQL and also offers protection against SQL injection (just in case the email passed is input by a user).
this version of the method takes 7 parameters :-
The table name as a string
The columns to be extracted as an array of Strings (aka String array). null can be all columns.
The where clause less the WHERE keyword with ?'s to represent arguments (see next). null if no WHERE clause.
The arguments to be applied (replace ?'s 1 for 1) as a String array. null if none or no WHERE clause.
The GROUP BY clause, less the GROUP BY keywords. null if no GROUP BY clause.
The HAVING clause, less the HAVING keyword. null if no HAVING clause.
The ORDER BY clause, less the ORDER BY keywords. null if no ORDER BY clause.
SQLiteDatabase - query
- Note there are 4 query methods (see link for the subtle difference, I believe this is the most commonly used)
The data extraction is the new code. When a Cursor is returned it is at a position BEFORE THE FIRST ROW, so you need to move to a valid row. So the moveToFirst* method is suitable (note that if a move cannot be made by a move method that it will return false, hence how you can say if (cursor.moveToFirst())). The data is then extracted from the appropriate column use the **getString method, which takes an int as an argumnet for the column offset (0 in this case). However, using hard coded values can lead to issues so the getColumnIndex method is used to get the offset according to the column name (-1 is returned if the named column is not in the Cursor).

Why Sqlite return only last row not all rows data?

I don't know what's wrong with my code I follow the rule but I get wrong result. I want to search db and find all rows data but I only get last row from sqlite. my code to search database is bellow:
public ArrayList<ArrayList<ContractSaveDataFromDB>> ActiveContractData(String phone, String numberId)
{
ArrayList<ContractSaveDataFromDB> UserData = new ArrayList<ContractSaveDataFromDB>();
ArrayList<ArrayList<ContractSaveDataFromDB>> SendUserData =
new ArrayList<ArrayList<ContractSaveDataFromDB>>();
SQLiteDatabase db = this.getReadableDatabase();
String whereClause = "phone = ? AND numberId = ?";
String[] whereArgs = new String[]{
phone,
numberId
};
String orderBy = "activeContract";
Cursor res2=db.query("usersAccount",null,whereClause,whereArgs,null,null,orderBy);
res2.moveToFirst();
do{
UserData.clear();
int index;
ContractSaveDataFromDB contractSaveDataFromDB=new ContractSaveDataFromDB();
index = res2.getColumnIndex("buyAmount");
String buyAmount = res2.getString(index);
contractSaveDataFromDB.setBuyAmount(buyAmount);
UserData.add(contractSaveDataFromDB);
SendUserData.add(UserData);
} while(res2.moveToNext());
res2.close();
db.close();
return SendUserData;
I don't know what's wrong. I appreciate if you help me to solve my problem.

you already added where clause so maybe it is filtering your results try to remove it by change this
Cursor res2=db.query("usersAccount",null,whereClause,whereArgs,null,null,orderBy);
to this
Cursor res2=db.query("usersAccount",null,null,null,null,null,orderBy);

I believe that your issues is that you are trying to use an ArrayList of ArrayList of ContractSaveDataFromDB objects.
I believe that an ArrayList of ContractSaveDataFromDB objects would suffice.
It would also help you if you learnt to do a bit of basic debugging, as an issue could be that you are not extracting multiple rows.
The following is an alternative method that :-
uses the ArrayList of ContractSaveDataFromDB objects,
introduces some debugging by the way of writing some potentially useful information to the log
and is more sound, as it will not crash if no rows are extracted
i.e. if you use moveToFirst and don't check the result (false means the move could not be accomplished) then you would get an error because you are trying to read row -1 (before the first row) as no rows exists in the cursor.
:-
public ArrayList<ContractSaveDataFromDB> ActiveContractData(String phone, String numberId) {
ArrayList<ContractSaveDataFromDB> SendUserData = new ArrayList<ContractSaveDataFromDB>();
SQLiteDatabase db = this.getReadableDatabase();
String whereClause = "phone = ? AND numberId = ?";
String[] whereArgs = new String[]{
phone,
numberId
};
String orderBy = "activeContract";
Cursor res2 = db.query("usersAccount", null, whereClause, whereArgs, null, null, orderBy);
Log.d("RES2 COUNT", "Number of rows in Res2 Cursor is " + String.valueOf(res2.getCount()));
while (res2.moveToNext()) {
ContractSaveDataFromDB current_user_data = new ContractSaveDataFromDB();
current_user_data.setBuyAmount(res2.getString(res2.getColumnIndex("buyAmount")));
Log.d("NEWROW", "Adding data from row " + String.valueOf(res2.getPosition()));
SendUserData.add(current_user_data);
}
res2.close();
db.close();
Log.d("EXTRACTED", "The number of rows from which data was extracted was " + String.valueOf(SendUserData.size()));
return SendUserData;
}
If after running you check the log you should see :-
A line detailing how many rows were extracted from the table
A line for each row (if any were extracted) saying Adding data from row ? (where ? will be the row 0 being the first)
A line saying The number of rows from which data was extracted was ? (? will be the number of elements in the array to be returned)

I can't get data from database using cursor

I have make following function for getting data.
public List<Presentation> getSlideMaster() {
List<Presentation> pptList = new ArrayList<Presentation>();
String selectQuery = "SELECT * FROM "
+ Constants.SLIDE_MASTER.slideMaster_Table + " WHERE dm_Id=" + lastDeckID;
SQLiteDatabase db = dbhelper.getWritableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
if (cursor.moveToFirst()) {
do {
Presentation presentation = new Presentation();
presentation.setSlideId(cursor.getString(0));
getSlideID = presentation.getSlideId();
Log.i("string slide id in database helper", "" + presentation.getSlideId());
pptList.add(presentation);
} while (cursor.moveToNext());
}
String selectQuery2 = "SELECT sl_Id FROM "
+ Constants.SLIDE_LAYOUT.slideLayout_Table + " WHERE sm_Id = "
+ getSlideID;
Cursor cursorSL = db.rawQuery(selectQuery2, null);
Log.i("query", ""+selectQuery2);
if(cursorSL.moveToFirst()){
Log.i("getslideLayout function", "");
do{
Log.i("query string 0 ", ""+cursorSL.getString(0));
Presentation presentation = new Presentation();
presentation.setSlideLayoutId(cursorSL.getString(0));
getSlideLayoutId = presentation.getSlideLayoutId();
Log.i("string slide layout id in slideMaster", "" + getSlideLayoutId);
}while(cursorSL.moveToNext());
}
else{
Log.i("No Data Found!!!!!", "");
}
cursor.close();
cursorSL.close();
db.close();
return pptList;
}
I getting data from slideMaster_Table very fine and easily but I can't get data from another query, which is not print any value in Logcat inside of if(cursorSL.moveToFirst()) condition
When I use code in another activity i can get sl_Id very easily.

may below solution solve your problem
use Cursor cursorSL = db.rawQuery(selectQuery2, new String[]{getSlideID});
for
selectQuery2="SELECT sl_Id FROM "+Constants.SLIDE_LAYOUT.slideLayout_Table + " WHERE sm_Id = ?";

My speculation is that you have troubles constructing the second query. Basically it is never a good idea to construct database queries like you do. The android database API is providing more accurate interface for that. Rewrite your second part of program to:
String [] selectArgs = {getSlideID};
String selectQuery2 = "sm_Id = ?";
Cursor cursorSL = db.query(Constants.SLIDE_LAYOUT.slideLayout_Table, null,
selectQuery2, selectArgs, null, null, null, null);
Note that the fourth parameter of query is meant for substitution of where arguments, it is String[] and all the array members are substituted in sequence in the places of ? in the query string.
I think you might be facing problem with constructing the query.
PS: You are also misusing the log tags:
Log.i("No Data Found!!!!!", "");
Should actually be Log.i("TAG", "No Data Found!!!!!");
The first parameter is log tag and is supposed to be used for grouping related log messages, in your case you print every message in its own group, which does not make much sense.
I know this note will not solve your immediate problem, but I am pointing it out, so that you will know it for the future (I also suffer from seeing colleagues of mine learning from SO wrong practises like that one).

Cursor Index Out of Bounds Exception: Index -1 requested with size 0

I am just trying to search for the data in multiple table.If the where condition data is not present in first table(tab1) then it has to search in the second table(tab2) but I am getting the exception showing that
Cursor Index Out of Bounds Exception: Index -1 requested with size 0
Here is my code
SQLiteDatabase db=openOrCreateDatabase("train",SQLiteDatabase.CREATE_IF_NECESSARY, null);
Cursor c1;
String[] table={"tab1","tab2","tab3","tab4"};
int i=0;
do {
c1 = db.rawQuery("select * from '"+table[i]+"' where name='Triplicane'", null);
i++;
} while(c1 == null);
int id1=c1.getInt(0);
String nam1=c1.getString(1);
Toast.makeText(fare.this,"ID no:"+id1, Toast.LENGTH_LONG).show();
Toast.makeText(fare.this,"name"+nam1, Toast.LENGTH_LONG).show();

So from the beginning. Implicitly, each Cursor is positioned before first row so if you want to work with it you need to call
cursor.moveToFirst()
that moves Cursor to first row if is not empty and then is ready for work. If Cursor is empty simply it returns false. So how i mentioned now this method is very handy indicator whether your Cursor is valid or not.
And as my recommendation i suggest you to change your code because i think is broken and it sounds like "spaghetti code"
Cursor c = null;
String[] tables = {"tab1", "tab2", "tab3", "tab4"};
for (String table: tables) {
String query = "select * from '" + table + "' where name = 'Triplicane'";
c = db.rawQuery(query, null);
if (c != null) {
if (c.moveToFirst()) { // if Cursor is not empty
int id = c.getInt(0);
String name = c.getString(1);
Toast.makeText(fare.this, "ID: " + id, Toast.LENGTH_LONG).show();
Toast.makeText(fare.this, "Name: " + name, Toast.LENGTH_LONG).show();
}
else {
// Cursor is empty
}
}
else {
// Cursor is null
}
}
Notes:
Now i want to tell you some suggestions:
An usage of parametrized statements is very good practise so in a
future if you will work with statements, use placeholders in them. Then your statements becomes more human-readable, safer(SQL Injection) and faster.
It's also a very good practise to create static final fields that will hold
your column names, table names etc. and to use
getColumnIndex(<columnName>) method to avoid "typo errors" which are looking for very bad.

Your Cursor flag to empty row , On Sqlite cursor pointed to row number -1 ,
then if you use c.moveNext() or c.moveToFirst() you'll be able to read rows "row by row "

write cursor.movetoFirst() before getting data from cursor.

Android: Deleting specific row in database

Sorry if this seems obvious. I'm trying to write a method to delete a row from a String showId. What would be the best way, and can Cursors only be used for Selects or also for Deletes and Updates?
These are the two methods I'm at so far:
public int deleteShowById1(String showId){
Cursor cursor = db.rawQuery("DELETE FROM tblShows WHERE showId = '" + showId+"'", null);
if (cursor.moveToFirst()) {
return 1;
} else
return -1;
}
public int deleteShowById2(String showId) {
String table_name = "tblShows";
String where = "showId='"+showId+"'";
return db.delete(table_name, where, null);
}

As we know from mysql query, it is same here in android.
String query = "DELETE FROM " +TABLE_NAME+ " WHERE " + COLUM_NAME+ " = " + "'"+VALUE +"'" ;
SQLiteDatabase db = this.getWritableDatabase();
db.execSQL(query);
db.close();
VALUE may or may not have single quotation depending on datatype.

I tend to use the second method (db.delete), as I think using rawQuery is frowned upon.
If you do a select, then loop through the cursor to do updates or deletes, that would make sense, but to pass a cursor to do the delete or update doesn't make sense to me, as the program won't know how to parse the cursor results to get the correct fields.