Oracle：为其他两列的唯一组合添加增量ID

Question

I have a table which looks like this

Seq ID | Uid | Type | URL

for each Uid I can have multiple Urls for any given type, for example

Uid 123 can have 5 video urls and 6 image type urls

I want to insert auto incrementing seq id for each combination of Uid and Type so in the previous example the seq id of uid 123 and type video will go 1,2,3,4,5 for each video url and 1,2,3,4,5,6 for each image type url , and same for all the other uid and type combinations.

Answer 1

I would refrain from trying to store this kind of artificial construct in the database. If needed, it can be generated at query time:

SELECT Uid, Type, URL,
       ROW_NUMBER() OVER(PARTITION BY Uid, Type ORDER BY URL) AS SeqID
    FROM YourTable

Answer 2

Can you just do this in a query?

select row_number() over (partition by uid, type order by url) as seqID, . . .
from table

You can also do this in an update, for an after-the-fact update:

with toupdate as (
     select row_number() over (partition by uid, type order by url) as newseqID, . . .
     from table
)
update toudpate
    set seqID as newseqID

If you want to do it as part of an insert, you'll need to create a trigger to maintain the column values.