How to do a simple search in string in Firebase database?

In my case I was able to partly achieve a SQL LIKE in the following way:

databaseReference.orderByChild('_searchLastName')
                 .startAt(queryText)
                 .endAt(queryText+"\uf8ff")

The character \uf8ff used in the query is a very high code point in the Unicode range (it is a Private Usage Area [PUA] code). Because it is after most regular characters in Unicode, the query matches all values that start with queryText.

In this way, searching by "Fre" I could get the records having "Fred, Freddy, Frey" as value in _searchLastName property from the database.

Create two String variables

    searchInputToLower = inputText.getText().toString().toLowerCase();

    searchInputTOUpper = inputText.getText().toString().toUpperCase();

Then in the Query set it to:

    DatabaseReference reference = FirebaseDatabase.getInstance().getReference().child("Products");//Your firebase node you want to search inside..

    FirebaseRecyclerOptions<Products> options =
            new FirebaseRecyclerOptions.Builder<Products>()//the Products is a class that get and set Strings from Firebase Database.
            .setQuery(reference.orderByChild("name").startAt(searchInputUpper).endAt(searchInputLower + "\uf8ff"),Products.class)
            .build();

the "name" it's the node inside the Products Main Node.

the .startAt(searchInputUpper) & .endAt(searchInputLower + "\uf8ff") to make the search as contains all characters that typed in the inputText.getText() that you get.