Develop Reference

Search in sqlite database by criterias selected with checkbox

I have in my app a database with two tables : country and rights. Long story short, the db tells me whether a right (there is 10 rights in total) is legal or not in a specific country.
Now, I want the user to be able to search in my db by criterias. I have a layout with checkbox. If the user check a box, it mean he want to see every country in where the right is legal. For exemple, if he check the box "criteria1" and "criteria6", the user want the list of every country where criteria1 and criteria6 are legal, but we don't care wether the other rights are legal or not.
I asigned values to the checkboxs (1 if legal, 0 if illegal, just like in my db) and passes all of them to the activity who display the result of the search.
My problem is, I can't figure out how to search in my database. I need to only get the country where where the selected criters are equal to 1, but I don't know how to formulate my sql request (since I never know which criterias are going to be checked or not). My request need to only be about the criterias who has the value 1.
I had the idea of sending all my values to a function (witch returns a cursor) where I excecute a select statement if the value is equal to one, but I don't know how I could join all the result of my selects in a cursor. I also thought about using "CASE WHEN..." but it doesn't seem to work.
Does anyone have a clue on how I could deal with my search ?
If you need precisions on my problem, please ask.

This guy here (https://www.youtube.com/watch?v=NGRV2qY9ZiU&list=PL200JxfhYIgCrrpH4rCz-uNfBTb5sng1e) has the right idea.
The clip may be a bit slow but it does exactly what you want.
He creates a custom string based on if checkbox is checked and removes it from the string if unchecked.
To get what you want, you need to do a couple of things.
First, create a table with countries as rows, and rights as columns. Add 1 for right is present in country and 0 if not. Get this into an sqlite database (eg import via csv in DB browser for SQLite, free software; don't forget to create the android_metadata table in the sqlite database - search online for this). Import the database in the app (there is plenty of documentation for this online).
Second, change the text inputed in the if/else checkbox part of the script (he writes fruit names, you write for ex. "right1 = 1", or the exact query the checkbox should do on the column right1).
You also need to pay attention to the selection.add and selection.remove (know that selection is an array list which will store all your criteria for search by column).
Third, you need to change the content of his finalSelection (View view).
Delete all he has written and just create two strings:
String final1 = android.text.TextUtils.join(" or ", selection);
String final2 = "select country from table where " + final1;
The string final2 is your key for a cursor with a rawQuery. Just create a cursor in the database and pass the key to it. This can be done easily.
PS the method android.text.TextUtils.join() is amazing :)
You can place the operator of choice there.
If you need more than one operator (and, or etc), you can create different ArrayLists which you fill in the if/else checkbox is filled and join later in the finalSelection.

Oh, btw, if you have too many checkboxes, you will get a warning in the XML file (layout has more than 80 views is bad for performance).
In order to get around that, you need to get to know grid views a bit better. After reading a few tutorials on the basic use of GridViews, a good start for checkboxes inside them is here.
It may seem like a lot, but you need to learn to use holders to get information out of the getView of the modified BaseAdapter.
If you want to understand it better, follow the arrPath.
It is a String[] filled with all the paths of images found inside the cursor (string values from the dataColumnIndex, which contains paths of images).
Within the onClick() listener of the Button, from the arrPath he extracts only the rows of the cursor that were selected by checkbox click (thumbnailsselection[i] is a boolean - with a value TRUE/FALSE for each row in the cursor).
The selected paths are placed in the selectImages String, separated by OR.

Firebase query implementation

If we query data from Firebase on a key for a child node, does it downloads the whole child node and filter data in the application or it downloads the query specific data? i.e. the filtered data
String myUserId = getUid();
Query myTopPostsQuery = databaseReference.child("user-posts").child(myUserId).orderByChild("starCount");
myTopPostsQuery.addChildEventListener(new ChildEventListener() {});
myTopPostsQuery will sort data according to starCount and I will receive data in the addChildEventListener() I want to know that whether this data is being filtered inside my app after receiving or my app downloads only the filtered data from the Firebase.

If you use a filter in your query you will download the query specific data without any operation executed on the client side.
Keep in mind that:
You can only use one order-by method at a time. Calling an order-by method multiple times in the same query throws an error.
You can combine multiple limit or range functions. For example, you can combine the startAt() and endAt() methods to limit the results to a specified range of values.
For any other info take a read here

You get the data already filtered. When you use a query, let say, limitToLast(10) you get only those 10 elements. This is happening also in your case with orderByChild("starCount"). In your SnanpShot will find only those filtered elements. Please visit official doc for more details.
Hope it helps.

Based on the code you pasted here, your query will just retrieve all the posts for the database path user-posts/<id> with an ordered manner which means that there is not filter. But still you will get back all the available posts under the path you are querying. It can be a "semi-filter" as it will find only the posts which include starCount field
The best thing is to filter during your query in order to retrieve back exactly what is needed and not everything as you are doing right now, imagine that this list of posts can be really big so you will have a big issue with performance later.
Read the following section here about sorting & filtering.
https://firebase.google.com/docs/database/admin/retrieve-data#orderbychild
Apart from that consider to add an index in userId field for speeding up your query.

Natural sorting of alphanumeric values in sqlite using android

I have a list of names of starts with characters and end with numbers like: -
ka1, ka10, ka 2, ka, sa2, sa1, sa10, p1a10, 1kb, p1a2, p1a11, p1a.
I want to sort it in natural order, that is: -
1kb, ka, ka1, ka 2, ka10, p1a, p1a2, p1a10, p1a11, sa1, sa2, sa10.
The main problem I am seeing here is no delimiter between text and numeric part, there also a chance of without numeric part also.
I am using sqlite in android, I can do sorting using java after fetching points by cacheing cursor data, but I am using(recommended to use) cursor adapter.
Please suggest a query for sorting or is there any way to apply sorting in cursor?

I tried below query for Natural sorting:
SELECT
item_no
FROM
items
ORDER BY
LENGTH(item_no), item_no;
It worked for me in Sqlite db too. Please see this link, for more details.

I can propose using regex replacement adding zeros, creating temporary table of original and corresponding values, then follow this link for sorting it: http://www.saltycrane.com/blog/2007/12/how-to-sort-table-by-columns-in-python/
tip for regex add as many zeros after last letter, but limit the number of total digits for predicted maximum number of digits. If You need help with regex as well, provide exact info of valid and invalid values, so can halp with that too.
PS if want to be sure that zeros goes before last digits search for char from the end

Updated
You can use different ways - Some of are mentioned below:
BIN Way
SELECT
tbl_column,
BIN(tbl_column) AS binray_not_needed_column
FROM db_table
ORDER BY binray_not_needed_column ASC , tbl_column ASC
Cast Way
SELECT
tbl_column,
CAST(tbl_column as SIGNED) AS casted_column
FROM db_table
ORDER BY casted_column ASC , tbl_column ASC
or try the solution:
There are a whole lot of solutions out there if you hit up Google, and
you can, of course, just use the natsort() function in PHP, but it's
simple enough to accomplish natural sorting in MySQL: sort by length
first, then the column value.
Query: SELECT alphanumeric, integer FROM sorting_test ORDER BY LENGTH(alphanumeric), alphanumeric from here

How to retrieve data from more than one table in parse.com

I put my data in 3 tables(Links, Images and PDF)
each table has columns(university, faculty, grade, and description,...)
I want to retrieve description column in the 3 tables.
where university, faculty, and grade equal to certain values.
and sort them with creation date.
how can I perform that query in parse?

I'm not familiar with Android, but I'm pretty sure Parse does not support "Join" in the way a SQL database does. You could nest the queries, performing the next one in the previous one's completion block.
However, if you regularly want to get data from those 3 tables, I'd suggest you make it 1 table instead, with a column "Content" instead of Link/Img/PDF. Images and PDFs would probably be stored as PFFiles anyway, and you can put link as either its own string column or putting it in a file. You could also add a column "type" if you want to be able to query a specific type, or just keep track of which columns contains which data.
Then you could query the "Content" class, on the keys you want.

I think this link might help you
https://parse.com/docs/js/guide#relations and it is quite simple and nicely explained . You can't do it directly in the database, though.

Search data from sqlite3 database in android

I have a Sqlite3 database in android, with data are sentences like: "good afternoon" or "have a nice day", now I want to have a search box, to search between them, I use something like this :
Cursor cursor = sqliteDB.rawQuery("SELECT id FROM category WHERE sentences LIKE '"+ s.toString().toLowerCase()+ "%' LIMIT 10", null);
But it only show "good afternoon" as result if user start searching with first "g" or "go" or "goo" or etc, how can I retrieve "good afternoon" as results, if user search like "a" or "af" or "afternoon".
I mean I want to show "good afternoon" result, if user search from middle of a data in sqlite3 db, not only if user searches from beginning.
thanks!

Just put the percent sign in front of your query string: LIKE '%afternoon%'. However, your approach has two flaws:
It is susceptible to SQL injection attacks because you just insert unfiltered user input into your SQL query string. Use the query parameter syntax instead by re-writing your query as follows:
SELECT id FROM category WHERE sentences LIKE ? LIMIT 10. Add the user input string as selection argument to your query method call
It will be dead slow the bigger your database grows because LIKE queries are not optimized for quick string matching and lookups.
In order to solve number 2 you should use SQLite's FTS3 extension which greatly speeds up any text-related searches. Instead of LIKE you would be using the MATCH operator that uses a different query syntax:
SELECT id FROM category WHERE sentences MATCH 'afternoon' LIMIT 10
As you can see the MATCH operator does not need percent signs. It just tries to find any occurrence of a word in the whole text that is being searched (in your case the sentences column). Read through the documentation of FTS3 I've linked to. The MATCH query syntax provides some more pretty handy and powerful options for finding text in your database table which are pretty similar to early search engine query syntax such as:
MATCH 'afternoon OR evening'
The only (minor) downside to the FTS3 extension is that it blows up the database file size by creating additional search index tables and meta-data. But I think it's well worth it for this use case.