NOT NULL columns in SQLite and error catching - android

I have a database that is being filled by user defined EditTexts. None of the edit texts should allow empty fields. I know that I can check for this with a couple simple if-statements: if myEditText.getText().toString().equals("") // display error. However I would perfer to use this opportunity to brush up on my SQLite and error catching (as demonstrated in my add method). How would I go about altering the columns in the table below to NOT NULL and generating/catching an error when a user attempts to add/update with empty fields?
My database table:
db.execSQL("CREATE TABLE inventory (category TEXT, itemNum TEXT, quantity INTEGER, price REAL, image INTEGER, UNIQUE(category, itemNum) ON CONFLICT FAIL);");
My add method:
... fill ContentValues values
try{
db.getWritableDatabase().insertWithOnConflict(DatabaseHelper.TABLE_NAME, DatabaseHelper.CATEGORY, values, SQLiteDatabase.CONFLICT_FAIL);
fillItemNumbers();
}
catch(SQLiteConstraintException e)
{
Toast
.makeText(MyActivity.this, etItemNum.getText().toString() + " already exists in " + catSpinner.getSelectedItem().toString() +". Consider using Update.",Toast.LENGTH_LONG)
.show();
}
My update method:
... fill ContentValues values
String[] args = {catSpinner.getSelectedItem().toString(), etItemNum.getText().toString()};
int rowsAffected = db.getWritableDatabase().update(DatabaseHelper.TABLE_NAME, values, DatabaseHelper.CATEGORY + "=? AND " + DatabaseHelper.ITEM_NUMBER + "=?" , args);
UPDATE:
I did a little digging and came up with this:
db.execSQL("CREATE TABLE inventory (category TEXT NOT NULL, itemNum TEXT NOT NULL, quantity INTEGER NOT NULL, price REAL NOT NULL, image INTEGER NOT NULL, UNIQUE(category, itemNum) ON CONFLICT FAIL);");
Is this what I am looking for? If so, how can I use this to my advantage (see above)?

I am not sure if you can actually Alter Column Definition for table. I know you can Alter Table itself, like adding new Column to Table. You might need little trick to modify your database if there is lot of data in it that you want to preserve.
One way to it to create new table and try copying data to new table and afterwards remove old table and rename new Table. It's not most efficient way to do it but it'll get the job done though.
http://www.sqlite.org/lang_altertable.html
EDIT
Here you go
CREATE TABLE inventory (category TEXT not null, itemNum TEXT not null, quantity INTEGER not null, price REAL not null, image INTEGER not null, UNIQUE(category, itemNum) ON CONFLICT FAIL);
EDIT 2
Try this
CREATE TABLE inventory (category TEXT not null ON CONFLICT FAIL, itemNum TEXT not null ON CONFLICT FAIL, quantity INTEGER not null ON CONFLICT FAIL, price REAL not null ON CONFLICT FAIL, image INTEGER not null ON CONFLICT FAIL, UNIQUE(category, itemNum) ON CONFLICT FAIL);

All you need to do is set the columns to NOT NULL.
Then use
insertWithOnConflict(String table, String nullColumnHack, ContentValues initialValues, int conflictAlgorithm)
and
updateWithOnConflict(String table, ContentValues values, String whereClause, String[] whereArgs, int conflictAlgorithm)`
There are several constants you can use for the conflictAlgorithm, depending on exactly what you want to happen. If you want to simply not enter the data into the table, CONFLICT_IGNORE will do the trick. If you want a return code letting you know so you can act on it (let the user know) then you might want CONFLICT_FAIL.
See this for further information.
Hope this helps.

Related

android second column returns no value

I have a problem to create a table. If I try to get a value from the second column, android writes a empty space in the toast. But if I try to get a value from the first column, android writes the value of the column correctly. The query functions to write the first column and to write the second column are equal. So I think the Creation of the Table is the problem. But look yourself:
public SQLiteDatabase tabelleerstellen(){
SQLiteDatabase leveldatabase = openOrCreateDatabase("leveldata.db",SQLiteDatabase.CREATE_IF_NECESSARY, null);
leveldatabase.setVersion(1);
final String CREATE_TABLE_LEVEL =
"CREATE TABLE IF NOT EXISTS tbl_level ("
+ "id INTEGER PRIMARY KEY AUTOINCREMENT, "
+ "ME1 TEXT, "
+ "ME2 TEXT, "
+ "ME3 TEXT, "
+ "ME4 TEXT, "
+ "ME5 TEXT, "
+ "ME6 TEXT, "
+ "ME8 TEXT, "
+ "GESCHAFFT INTEGER);";
leveldatabase.execSQL(CREATE_TABLE_LEVEL);
return leveldatabase;
}
public void tester(SQLiteDatabase leveldata){
ContentValues cursortester = new ContentValues();
cursortester.put("ME2","25");
leveldata.insert("tbl_level",null,cursortester);
String[] testerpr = {"ME2"};
Cursor testerprüfen = leveldata.query("tbl_level",testerpr,null,null, null, null,null,null);
testerprüfen.moveToFirst();
String dada = testerprüfen.getString(testerprüfen.getColumnIndex("ME2"));
Toast testertoast = Toast.makeText(getApplicationContext(),dada,Toast.LENGTH_SHORT);
testertoast.show();
}
Please check the following things:
Please make sure the table is up to date .. so try to call DROP TABLE IF EXISTS tbl_level; and recreate the table.
If you run a test make sure the table is completely empty ... so delete everything at the beggining of the test.
If the table can contain elements during the test then make sure you check the last inserted element. Please note that calling testerprüfen.moveToFirst(); moves the cursor to the first row in the table so checking that row every time is even if the table contains 50 elements is not a good thing. In this case you either use a sorting option in your query of uese while (testerprüfen != null && testerprüfen.moveToNext()) {// Your code here}
All in all I think your problem is that you already inserted more that one element in the able but you always check only the first element (with testerprüfen.moveToFirst();). Please not that there is a cursor.moveToLast() method that you can also call. This method moves the cursor to the last row in the table.

Delete specific record in sqlite table based on two criteria: _id and column

I have created a sqlite table for my android app, this table has 5 columns and multiple rows, the columns being: _id, column1, column2, column3, column4.
I want to delete a specific record, for instance the record stored in column3 corresponding to _id (in a different class are the getters and setters, for this I've named the class "TableHandler")
I guess that I'm a bit confused, following is what I was planning, but for column3 I'm not sure what should be the argument, I just want to delete whatever is in that column position corresponding to _id
public void deleteValueColumn3(TableHandler value){
SQLiteDatabase db = this.getWritableDatabase();
db.delete(TABLE_NAME, KEY_ID + " = ? AND " + KEY_COLUMN3 + " = ?",
new String[] {String.valueOf(value.getID()), ?????????);
db.close();
}
The ???????? is that I'm stuck there, maybe the whole method needs to be rewritten, I would appreciate your input.
Thanks
If you want to delete the whole record, just use the _id of the record in delete method, because that is the primary key for your table and therefore is unique. If you'd rather keep the record, you con always use the SQLiteDatabase.update method, specifying null as the new value that will replace column3 value; check out that column3 declaration has no NOT NULL tag, otherwise that could easily throw exception at you.
SQLite does not allow you to delete columns for a specific row.
You can only delete ROWS of data (delete the row that has the column _ID = 1).
Here's a quick tutorial on SQL.
How about updating that column with a null value, rather than using delete()?
ContentValues cv = new ContentValues();
cv.putNull(KEY_COLUMN3);
db.getWritableDatabase().update(
TABLE_NAME,
cv,
KEY_ID + "=?",
new String[]{String.valueOf(keyIdValue)});

Sqlitedatabase query not working when selecting by _id

I've been stuck on this problem with my sqlitedatabase for several days now.
My insert method works, I break after it has been run and check that the database now contain rows (before it was empty), by querying for the entire database, which works.
This is the insert method which returns the generated puzzleId.
public int savePuzzleToEdit(ContentValues puzzle, Integer puzzleId) {
Integer id = puzzle.getAsInteger(General.ID);
if (id == 0 && puzzleId == null) {
puzzle.remove(General.ID);
puzzleId = (int) ourDatabase.insert(PUZZLE_TABLE, null, puzzle);
}else {
....
}
return puzzleId
The query method however, does not return any results, aka the cursor is empty.
public ArrayList<ContentValues> getCreatedPuzzles(int puzzleId) {
Cursor c = ourDatabase.query(PUZZLE_TABLE, null, "_id = " + puzzleId, null, null, null, null, null);
while (c.moveToNext()) { // Generate return list ...}
I have tried breaking after the insert and before the query in order to see if there is indeed rows in the database, which there is. I am however not able to query by selecting by id. I can however, query by the other fields in the table and get the correct rows as a result, so it has to be the _id field which has an error.
I have also tried to use the rawQuery method which also works when querying for the entire database or by any of the other fields but id.
This is the create statement:
private static final String PUZZLE_TABLE_CREATE =
"CREATE TABLE puzzle ( _id INTEGER, name varchar(45), category " +
"varchar(25), publishdate DATE, rating INT, timesplayed INT, numberOfQuestions INT);";
As I understood it the id has to be INTEGER in order to auto_increment on insert, which I believe works since the insert method returns a id, which varies from one insert to another.
The query method does not return any errors or exceptions, and it just seems like there are no rows in the table with that id. I have assumed that the returned puzzleId is also being stored as the id in the table, but that might be wrong?!
Any and I mean any suggestions or insights on how to try to fix this problem is highly appreciated.
first thing first your create table statement might be wrong the _id will not autoincrement if you don't mention it in the statement. it should be like this
_id integer primary key autoincrement
and also check your create table statement for other errors

Android SQLite Join Query

I'm creating an app as a learning tool and am having difficulty with join queries.
I have a database with two tables- horses and covers- declared as follows;
private static final String HORSES_CREATE = "create table horses (_id integer primary key autoincrement, "
+ "name text not null, type integer not null, birthDate text not null, vaccineDate text not null, "
+ "inFoal integer not null, notes text not null);";
The 'type' field refers to stallion, mare, gelding etc and is selected from a spinner (populated from an XML String array).
private static final String COVERS_CREATE = "create table covers (_id integer primary key autoincrement, "
+ "stallionName integer not null, mareName integer not null, firstCoverDate text not null, lastCoverDate text not null, "
+ "scan14Date text not null, scan28Date text not null, foalingDate text not null, inFoal integer not null, notes text not null);";
stallionName is actually stored as the _id field of the horse from the horse table. It is selected from a spinner that only displays horses whose type defined as 'Stallion' in the horses table. (The same applies for Mare).
I have a class 'DatabaseHelper' to create and upgrade the tables, and each table has its own adapter class 'horsesDbAdapter' and 'coversDbAdapter' that contains the methods to add, edit and delete entries, and relevant queries. (fetchAllHorses(), fetchHorse(long rowId) )
eg:
public Cursor fetchAllHorses() {
return mDb.query(DATABASE_TABLE,
new String[] { KEY_ROWID, KEY_NAME, KEY_TYPE, KEY_BIRTHDATE,
KEY_VACCINEDATE, KEY_INFOAL, KEY_NOTES }, null, null,
null, null, null);
}
(It's all adapted from the Android notepad example)
I have the contents of the covers table displayed in a listview (just showing the stallionName and mareName). But as those fields just contain the unique reference to the horses table all that is displayed is the fairly uninformative _id field.
My question is; how can I get the relevant name for the horses to display in the listView? I've read up on join queries etc but get lost when I try implement them. I assume I have to join on horses._id and covers.stallionName (then make an almost-identical one for MareName) but I can't find a concrete example of how to do this.
Please let me know if any additional information/ code is needed.
Any help would be greatly appreciated, thankyou in advance.
EDIT:
I have made stallionName and mareName foreign keys referencing (_id) in the horses table, but am still unsure how and where to implement the join query; should it be in the horsesDbAdapter, coversDbAdapter or the coversList class? (coversList is the class that creates and populates the listView)
The covers table declaration now reads;
private static final String COVERS_CREATE = "create table covers (_id integer primary key autoincrement, "
+ "stallionName integer not null, mareName integer not null, firstCoverDate text not null, lastCoverDate text not null, "
+ "scan14Date text not null, scan28Date text not null, foalingDate text not null, inFoal integer not null, notes text not null," +
"FOREIGN KEY (stallionName) REFERENCES horses (_id), FOREIGN KEY (mareName) REFERENCES horses (_id));";
I'm a newbie to Android and SQLLiteHelper and was wondering about the same thing.
After reading this post, I found that the method to define joins between tables is done with the SQLLiteQueryBuilder.setTables method. See the reference here
I got this from this blog
Hope this helps pointing readers in the right direction.
I've managed to get it working. For anyone else who may have a similar problem I'll try detail what I did.
As #deceiver stated I should have made stallionName and mareName foreign keys referencing horses (see Edit).
In the coversList class (the class that implements the listView) I just needed to get an instance of the database and use a rawQuery to implement the SQL code directly (It may be possible to do it with Query but I'm not sure how)
The added code is as follows;
private Cursor coversCursor;
private void fillData() {
db = (new DatabaseHelper(this).getReadableDatabase());
coversCursor = db.rawQuery("SELECT horses1.name AS stallionNameText, covers.*, horses2.name AS mareNameText FROM horses horses1 JOIN covers ON horses1._id = covers.stallionName JOIN horses horses2 ON horses2._id = covers.MareName",
null);
startManagingCursor(coversCursor);
// Create an array to specify the fields we want to display in the list
// (the renamed fields from the above query)
String[] from = new String[] { "stallionNameText", "mareNameText" };
// and an array of the fields we want to bind those fields to (in this
// case just text1)
int[] to = new int[] { R.id.rowStallionName, R.id.rowMareName };
// Now create a simple cursor adapter and set it to display
SimpleCursorAdapter covers = new SimpleCursorAdapter(this,
R.layout.covers_list_row, coversCursor, from, to);
setListAdapter(covers);
}
FillData() is then called in the onCreate() method. Then just close the db in the onDestroy method.
(Selecting all columns from the covers table seems wasteful here but I will eventually show these columns in the listView aswell. I just wanted to answer this before continuing coding).
A tutorial I found helpful was http://coenraets.org/blog/android-samples/androidtutorial/
I had issues with the SQL query as there are 2 foreign keys referencing the same table and I wanted the listView to display both the stallion name and mare name, so had to join two horses table to a covers table. I just needed to rename the tables in the FROM section of the SQL query. Hopefully the above code is clear. If not, I found the following useful; http://www.bryantwebconsulting.com/blog/index.cfm/2005/3/11/join_a_table_to_itself_in_sql
Sorry if this explanation is too specific to my (unusual) example.
Thanks for reading.

Android SQLite Repeated Elements

I have an issue with SQLite on android. Right now, I'm pulling a JSON object from a server, parsing it, and putting each sub-object in a Table with things such as the Name, Row_ID, unique ID, etc. using this code:
public void fillTable(Object[] detailedList){
for(int i=0;i<detailedList.length;++i){
Log.w("MyApp", "Creating Entry: " + Integer.toString(i));
String[] article = (String[]) detailedList[i];
createEntry(article[0], article[1], article[2], article[3], article[4], article[5]);
}
}
createEntry does what it sounds like. It takes 6 strings, and uses cv.put to make an entry. No problems.
When I try to order them however, via:
public String[] getAllTitles(int m){
Log.w("MyApp", "getTitle1");
String[] columns = new String[]{KEY_ROWID, KEY_URLID, KEY_URL, KEY_TITLE, KEY_TIME, KEY_TAGS, KEY_STATE};
Log.w("MyApp", "getTitle2");
Cursor c = ourDatabase.query(DATABASE_TABLENAME, columns, null, null, null, null, KEY_TIME);
Log.w("MyApp", "getTitle3");
String title[] = new String[m];
Log.w("MyApp", "getTitle4");
int i = 0;
int rowTitle = c.getColumnIndex(KEY_TITLE);
Log.w("MyApp", "getTitle5");
for(c.moveToFirst();i<m;c.moveToNext()){
title[i++] = c.getString(rowTitle);
Log.w("MyApp", "getTitle " + Integer.toString(i));
}
return title;
}
Each entry actually has many duplicates. I'm assuming as many duplicates as times I have synced. Is there any way to manually call the onUpgrade method, which drops the table and creates a new one, or a better way to clear out duplicates?
Secondary question, is there any way to order by reverse? I'm ordering by time now, and the oldest added entries are first (smallest number). Is there a reverse to that?
If you don't want duplicates in one column then create that column with the UNIQUE keyword. Your database will then check that you don't insert duplicates and you can even specify what should happen in that case. I guess this would be good for you:
CREATE TABLE mytable (
_id INTEGER PRIMARY KEY AUTOINCREMENT,
theone TEXT UNIQUE ON CONFLICT REPLACE
)
If you insert something into that table that already exists it will delete the row that already has that item and inserts your new row then. That also means that the replaced row gets a new _id (because _id is set to automatically grow - you must not insert that id yourself or it will not work)
Your second question: you can specify the direction of the order of if you append ASC (ascending) or DESC (descending). You want DESC probably.
Cursor c = ourDatabase.query(DATABASE_TABLENAME, columns, null, null, null, null, KEY_TIME + " DESC");

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