Having a confounding problem with a query that worked for a while and then stopped working. With a try and catch, there is no error it just returns a null cursor?
Is there a GUI where you can run the query to check the result first or see an error, perhaps it is something subtle like keys? I have confirmed the data types but don't know where else to look. I have concerns going forward on how to debug this type of issue so would appreciate any direction you can offer.
Thanks in advance.
The code set works fine on a single table but when I join 2 tables it now fails (worked yesterday)
Working:
String selectQuery =
SELECT ou.*,"name" as Orchard_Name FROM " + TABLE_TP_ORCHARD_USER ou ;
not working in this case a joined query :
String selectQuery = "SELECT ou.tp_orchard_user_Orchard_ID as
tp_orchard_user_Orchard_ID,ou.tp_orchard_user_User_ID as
tp_orchard_user_User_ID,sd.Orchard_Name as Orchard_Name FROM " +
TABLE_TP_ORCHARD_USER + " ou JOIN " + TABLE_SD_ORCHARD + " sd on
ou.tp_orchard_user_Orchard_ID=sd.Orchard_Id" ;
I have run this code in mysql on another DB and it is fine; it seems maybe there is another error that eclipse can't display? Or I don't know how?
My code sample is:
SQLiteDatabase db = this.getReadableDatabase();
Cursor daCursor = db.rawQuery(selectQuery,null);
if (daCursor != null) {
if( daCursor.moveToFirst() ){
do{
// String Orchard_ID =
daCursor.getString(daCursor.getColumnIndex("Orchard_Id"));
String Orchard_ID = daCursor.getString(0);
Log.i("dbhandler fetchAllOrchards cursor Orchard_ID",
Orchard_ID);
Log.i("dbhandler fetchAllOrchards cursor Orchard_ID",
Orchard_Name);
} while (daCursor.moveToNext());
} else{
Log.i("cursor is false","fail");
}
}
Related
I am getting an error in Android Studio to do with my Cursor.
I have the following line in my code
String data = cursor.getString(cursor.getColumnIndex(columnIndex));
columnIndex is being passed into the method.
This part cursor.getColumnIndex(columnIndex) produces the following error
Value must be ≥ 0
Its happening in my DBHelper class and also my recycler adapter when it uses a cursor too.
It shows up as an error in red but the app still builds and runs without issue.
Any ideas?
Thanks for any help.
Update 22-Sep-21
I'm adding some code as requested and also how i have got around this error. Not sure if its the best way though.
So the method im using is this....
public String getTripInfo(String tableName, int tripNo, String columnIndex){
String data = "";
// Select all query
String selectQuery = "SELECT * FROM " + tableName + " WHERE " + TRIP_DETAILS_TRIP_NUMBER + "=" + tripNo;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// Looping through all rows and adding to list
if(cursor.moveToFirst()){
do{
data = cursor.getString(cursor.getColumnIndex(columnIndex));
} while(cursor.moveToNext());
}
// Closing connections
cursor.close();
db.close();
//Returning number plates
return data;
}
The error is in the do while loop. The part in red is "cursor.getColumnIndex(columnIndex))"
The way i have gotten around this error is using the following code instead
public String getTripInfo(String tableName, int tripNo, String columnIndex){
String data = "";
// Select all query
String selectQuery = "SELECT * FROM " + tableName + " WHERE " + TRIP_DETAILS_TRIP_NUMBER + "=" + tripNo;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(selectQuery, null);
// Looping through all rows and adding to list
if(cursor.moveToFirst()){
do{
int index = cursor.getColumnIndex(columnIndex);
data = cursor.getString(index);
} while(cursor.moveToNext());
}
// Closing connections
cursor.close();
db.close();
//Returning number plates
return data;
}
I had an error like this.
My solution : change method getColumnIndex into getColumnIndexOrThrow.
The problem is that cursor.getColumnIndex() can return -1, you're passing it as a direct parameter, and the cursor getters need a column index gte 0. The getters' parameter is annotated with #IntRange(from = 0) which is why lint marks it as an error.
So, even though you might have built your project such that it would never produce an invalid column index, the fact that such a possibly could exist is why lint is tagging it.
Your code revision only avoids the issue. It would be best to use cursor.getColumnIndexOrThrow() or test index for gte 0.
You can get away with your changes since you know more about your project than lint does, it just isn't the best practice.
Use This Method Proper Work :-
#SuppressLint("Range") Strong name = cursor.getString(cursor.getColumnIndex(indexNumber));
I'm a newbie with Android Studio so please be patient... This forum often leads me with suggestions and examples (as a reader), but today I decided to ask for help:
Since hours, I try to build an SQLite statement in Android Studio: There is a column COLUMN_LAST_ATTEMPT with date and time as String, e.g. 2020-01-09 17:23, see screenshot, and I want to get the newest date (without time) from the table, e.g. 2020-09-01. I tried various options but I can't get it to run.
What I need is an Android SQLite Statement for
SELECT MAX(SUBSTR(last_attempt,11,20)) FROM quiz_questions
(which runs on DBBrowser), where 'last attempt' is a column of table 'quiz_questions', screenshot of that column in table 'quiz_questions'
I tried the following rawQueries, none of them works:
In QuizDBHelper-Class
//...
final QuizDbHelper dbHelper = QuizDbHelper.getInstance(this);
//...
public String newestQuiz(){
db = getReadableDatabase();
String result = null;
Cursor cursor = db.rawQuery("SELECT MAX(" + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT + ") FROM "
+ QuizContract.QuestionsTable.TABLE_NAME, null);
//Cursor cursor = db.rawQuery("SELECT MAX(SUBSTR(" + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT +
// ",11,20)) FROM " + QuizContract.QuestionsTable.TABLE_NAME, null);
//Cursor cursor = db.rawQuery("SELECT " + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT + " FROM " +
// QuizContract.QuestionsTable.TABLE_NAME, null);
if(cursor.moveToFirst()){
do {
result = cursor.getString(c.getColumnIndex(QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT));
} while (cursor.moveToNext());
}
cursor.close();
return result;
}
In Statistics-Class
String LastUse = dbHelper.newestQuiz();
LastUsage.setText("Letzte Challenge: " + LastUse);
//LastUsage is a TextView in activity_Statistics.xml
//attached with LastUsage = findViewById(R.id.text_lastUsage);
Either the SQLite statements are totally wrong or I make (basic?) mistakes in statistics class. I need ...newbie help!
I need something like Select column from table where substring of date-Entry == newest
Your issue appear to be column names. That is a Cursor only contains the columns extracted, not all the columns from the table. Although you are basing your query on the column as per QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT that will not be the column name in the cursor.
Rather it will will MAX(SUBSTR(" + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT +
// ",11,20))
The simplest way of managing this is to give the column in the Cursor a specific name using AS. As such perhaps use :-
Cursor cursor = db.rawQuery("SELECT MAX(" + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT + ") AS " + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT + " FROM "
+ QuizContract.QuestionsTable.TABLE_NAME, null);
However, you may prefere to use a column name (AS ????) specififc to the situation e.g.
........ AS max_" + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT + ........
You would then have to use :-
result = cursor.getString(c.getColumnIndex("max_" + QuizContract.QuestionsTable.COLUMN_LAST_ATTEMPT));
Alternately, as it's just a single value/column that is returned in the cursor you could use the column offset of 0, in which case the column name is irrelevant as long as it is valid. However, using offsets is not typically recommended due to the lack of validation of the column being accessed.
re the comment :-
I just need the date part
As the date is a recognised DateTime format (and also that such formats are directly sortable/orderable), use max(date(column_name)) or even max(column_name).
I'm currently having an issue with my SQL Lite code with regards to counting matching results. In my application the user will have the ability to add a new folder and give it a name. Before the folder is added to the application my code will check to see if a folder with the same name already exists if so it will prompt the user.
When using my code below I receive an error informing me the column doesn't exist. If I remove everything past WHERE then it works perfectly and counts every record within the table.
I've reinstalled the application and changed the database version so that its completely clean, just to make sure. I'm certain its only something very minor I'm missing.
public int countMatchingFolders (String folderName){
String countQuery = "SELECT * FROM " + Primary_Table + " WHERE " + Col_FolderName + " = " + folderName;
SQLiteDatabase db = this.getReadableDatabase();
Cursor cursor = db.rawQuery(countQuery, null);
int cnt = cursor.getCount();
cursor.close();
return cnt;
}
Error message I'm receiving
android.database.sqlite.SQLiteException: no such column: testFolder (code 1): , while compiling: SELECT * FROM Folder_Table WHERE Col_FolderName = testFolder
Any assistance to help with the issue would be greatly appreciated.
The error is because the string value doesn't have quotes around it, so it is treated as a table name instead of a string. You should use a bound query argument to fix this. Bound arguments also prevent SQL injection attacks:
String countQuery = "SELECT * FROM " + Primary_Table + " WHERE " + Col_FolderName + " = ?";
Cursor cursor = db.rawQuery(countQuery, new String[]{folderName});
Note that you can do "SELECT COUNT(*) as row_count" ... to let the database engine count the number of records more efficiently.
My app is using an external SQLite database. The database is created using DB Browser for SQLite software. I am using the following method to query my table with the column ENGLISH (same as en_word). However, problem is the query is slow when my database become large.
public static final String ENGLISH = "en_word";
public static final String TABLE_NAME = "words";
String sql = "SELECT * FROM " + TABLE_NAME +
" WHERE " + ENGLISH + " LIKE ? ORDER BY LENGTH(" + ENGLISH + ") LIMIT 100";
SQLiteDatabase db = initializer.getReadableDatabase();
Cursor cursor = null;
try {
cursor = db.rawQuery(sql, new String[]{"%" + englishWord.trim() + "%"});
List<Bean> wordList = new ArrayList<Bean>();
while(cursor.moveToNext()) {
String english = cursor.getString(1);
String mal = cursor.getString(2);
wordList.add(new Bean(english, mal));
}
return wordList;
} catch (SQLiteException exception) {
exception.printStackTrace();
return null;
} finally {
if (cursor != null)
cursor.close();
}
I tried to create index using DB Browser for SQLite.
CREATE INDEX `kindx` ON `words` ( `en_word` )
However, do I need to modify my code so that my app will query the database using this index? If so, how to do that?
The problem is that SQLite, like most relational databases, can use an index when the parameter to a 'like' clause ends with a wildcard, it cannot use an index when the parameter begins with a wildcard.
So, for this type of query, the index will not be used, and you wind up with a full table scan. This is why it is slower with a large number of rows.
You are actually attempting to do what is known as "full text search", which is not really possible to do efficiently without database features to support it directly.
I have not tried it, but I see that SQLite does have full-text search capabilities, and that it is supported on Android. See Full text search example in Android for an example.
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).