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Running an update for 50% of records

Running an update for 50% of records

Running an update for 50% of records

I need to update the value in a column for 50% of the records in the table. I need to use a single sql for this. I am using the following but it does not work.

update a
set column_name = 'xxxxx'
where acct in
sel acct from a
sample .50

It fails with a message saying that I cannot use sample in a subquery.

Does anybody know of a way to do this?


RE: Running an update for 50% of records


Here is what i tried to update 50% of the records in a table. Hope this helps.

create table test123 (acct integer, b integer);
insert into test123 values(1,NULL);
insert into test123 values(2,NULL);
insert into test123 values(3,NULL);
insert into test123 values(4,NULL);

update test123
(select acct from test123 sample .50) as b
set b = 1
where test123.acct = b.acct

select * from test123;
 acct     b      
 -------  ------
 2        (null)
 4        1      
 1        (null)
 3        1  

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