I answered a question in stack overflow and the user that asked the question ask me:
SQlite Query in android using cursor
why i must give my selectionArgs an Array instead its a single value ?
I didn't think about this before and its my question too now.
We must use an array when we have only one value for selectionArgs in DB query?
(I hope i right my question in right place)
Here's the relevant documentation. Basically, String[] selectionArgs is an array so you can have one or more arguments for your sql WHERE clause. Since these parameters are used in the database.query() method, they're actually building a raw sql query string to be run by SQLite. In the String selection parameter, you specify all the WHERE clause column names, like this:
String selection = "DefaultId =? OR Name=?";
For every ? in selection, a corresponding WHERE value is substituted from your selectionArgs array. So, you should have something like this:
String[] selectionArgs = new String[]{"567", "Bob"};
The database.query() method iterates through selectionArgs for every ? it finds in selection. So, the array size should match the number of ? placeholders you're using in selection. (If there are more ? than selectionArgs values, then I believe nullgets substituted instead. I haven't verified this though.)
So basically, since it's possible to have multiple WHERE values substituted into selection, that's why selectionArgs is an array instead of a simple String.
? and one value for it why we must pass an array for it and not a string only ! I think an String array take more space in memory instead of a string value . i hope explain it clear :)
? altogether and place your values directly into String selection (e.g. String selection = "DefaultId=567". If you do this, just provide an empty array for the values, like this: String selectionArgs[] = new String[]{}