How to UPDATE a column to SET previous row value to NULL cells?

Question

I have a table as

id  value
1   music
2 
3   movie
4   
5
6   book
7
8

Some values are missing, and I want to assign the value of previous row to produce

id  value
1   music
2   music
3   movie
4   movie
5   movie
6   book
7   book
8   book

Answer 1

Sample schema and data

create table tbl (
  id int,
  value varchar(10)
  );
insert into tbl select
  1,   'music' union all select
  2,   ''  union all select
  3,   'movie' union all select
  4,   '' union all select
  5,   '' union all select
  6,   'book' union all select
  7,   '' union all select
  8,   '';

Query (SQL Fiddle)

update tbl join (
    select curr.id, (
        select prior.value
          from tbl prior
         where prior.value > ''
           and prior.id < curr.id
      order by prior.id desc
       limit 1) value
      from tbl curr
    where ifnull(curr.value,'') = ''
  ) g on g.id = tbl.id
set tbl.value = g.value;

Results

select * from tbl

| ID | VALUE |
--------------
|  1 | music |
|  2 | music |
|  3 | movie |
|  4 | movie |
|  5 | movie |
|  6 |  book |
|  7 |  book |
|  8 |  book |