Tuesday, December 04, 2018

Generate Serial Number for Existing Table

Table T_REVIEW has column id as the unique key and dt as the timestamp. I want to add a serial number to the table based on the order by dt and id. In the following scripts, I use window function row_number to generate the serial number and update the table.
alter table t_review add(seq number);

update t_review a set seq= (
with tbl as (select id, row_number() over(order by dt, id) rnk from t_review)
select rnk from tbl b 
where b.id=a.id

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