Displaying single date header about multiple rows (Recycleview) - sql

Question

Evening everyone
I've currently got a simple recycle view adapter which is being populated by an SQL Lite database. The user can add information into the database from the app which then build a row inside of the recycle view. When you run the application it will display each row with its own date directly above it. I'm now looking to make the application look more professional by only displaying a single date above multiple records as a header.
So far I've built 2 custom designs, one which displays the header along with the row and the other which is just a standard row without a header built in. I also understand how to implement two layouts into a single adapter.
I've also incorporated a single row into my database which simply stores the date in a way in which I can order the database e.g. 20190101
Now my key question is when populating the adapter using the information from the SQL Lite database how can get it to check if the previous record has the same date. If the record has the same date then it doesn't need to show the custom row with header but if its a new date then it does?
Thank you
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Follow up question for Krokodilko, I've spent the last hour trying to work your implementation into my SQL Lite but still not being able to find the combination.
below the is the original code SQL Lite line I currently use to simply gain all the results.
Cursor cursor = sqLiteDatabase.rawQuery("SELECT * FROM " + Primary_Table + " " , null);

Answer 1

First you must define an order which will be used to determine which record is previous and which one is next. As I understand, you are simply using date column.
Then the query is simple - use LAG analytic function to pick a column value from previous row, here is a link to a simple demo (click "Run" button):
https://sqliteonline.com/#fiddle-5c323b7a7184cjmyjql6c9jh
DROP TABLE IF EXISTS d;
CREATE TABLE d(
d date
);
insert into d values ( '2012-01-22'),( '2012-01-22'),( '2015-01-22');
SELECT *,
lag( d ) OVER (order by d ) as prev_date,
CASE WHEN d = lag( d ) OVER (order by d )
THEN 'Previous row has the same date'
ELSE 'Previous row has different date'
END as Compare_status
FROM d
ORDER BY d;
In the above demo d column is used in OVER (order by d ) clause to determine the order of rows used by LAG function.