'merge' rows if they are duplicated in a table - SQLite - sqlite

Question

Table is the following:
CREATE TABLE UserLog(uid TEXT, clicks INT, lang TEXT)
Where uid field should be unique.
Here is some sample data:
| uid | clicks | lang |
----------------------------------------
| "898187354" | 4 | "ru" |
| "898187354" | 4 | "ru" |
| "123456789" | 1 | <null> |
| "123456789" | 10 | "en" |
| "140922382" | 13 | <null> |
As you can see, I have multiple rows with where the uid field is now duplicated. I would like for those rows to be merged in a following way:
clicks fields are added, and lang fields are updated if their previous value was null.
For the data shown above, it would look something like this:
| uid | clicks | lang |
---------------------------------------
| "898187354" | 8 | "ru" |
| "123456789" | 11 | "en" |
| "140922382" | 13 | <null> |
It seems that I can find many ways to simply delete duplicate data, which I do not necessarily want to do. I'm unsure how I can introduce logic in SQL statements that does this.

Answer 1

First update:
update userlog
set
clicks = (select sum(u.clicks) from userlog u where u.uid = userlog.uid),
lang = (select max(u.lang) from userlog u where u.uid = userlog.uid)
where not exists (
select 1 from userlog u
where u.uid = userlog.uid and u.rowid < userlog.rowid
);
and then delete the duplicate rows that are not needed:
delete from userlog
where exists (
select 1 from userlog u
where u.uid = userlog.uid and u.rowid < userlog.rowid
);