Question

This is a duplicate of this question for Postgres Update records that satisfies a condition with incrementing number but I need a way that will work with SQLite3.

Snipping from the original question:

SNIP

I have a table in postgres like this:

Id    Name    local_site_id    local_id
1     A       2                
2     B       2
3     C       1
4     D       2
5     E       1

How do I update the table into this using SQL query:

Id    Name    local_site_id    local_id
1     A       2                1
2     B       2                2
3     C       1                
4     D       2                3
5     E       1                

Right now, the local_id field is empty for all the records. I want to update the local_id values with an incrementing number starting from 1 only for rows that have local_site_id=2 Is it possible using SQL?

END-SNIP

I tried this command from the answer there but it doesn’t work for SQLite3

update T set local_id=s.rn 
from (select id,row_number() over(order by id) as rn from T where local_site_id=2) s
where T.id=s.id;

How can I achieve this in SQLite3?

Answer 1

This should do it:

.mode column
.headers on

create table T (Id, Name, local_site_id, local_id);

insert into T values
    (1, 'A', 2, null),
    (2, 'B', 2, null),
    (3, 'C', 1, null),
    (4, 'D', 2, null),
    (5, 'E', 1, null);

update T set local_id = (
    select 
        case local_site_id
            when 2 then (select count(*) 
                         from T t2 
                         where t2.id <= t1.id and local_site_id=2)
            else null
        end
    from T as t1 where T.id=t1.id);

select * from T;

which returns:

Id          Name        local_site_id  local_id  
----------  ----------  -------------  ----------
1           A           2              1         
2           B           2              2         
3           C           1                        
4           D           2              3         
5           E           1