What is the most efficient way of removing repeated values in a table? Currently the script I am using only removes...
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duplicates, so it must be run multiple times if the records are triplicated, etc.
Let's say for example that table T has a column C that repeats several times. You want to remove the repeated values.
1) Create a temporary view.
create view V as select count(*) as CNT , C from T group by C having count(*) > 1;2) Create a temporary table.
create TABLE T2 as SELECT * from T3) Try this PL/SQL block.
declare cursor c_v is select C from V; FOR cv in c_v LOOP Insert into T2 SELECT * FROM T where T.C = cv.C and ROWNUM = 1; END LOOP;4) DELETE ALL repeated.
DELETE FROM T where C in (select C from V)5) Add only one repeated row.
insert into T select * from T2;6) Drop TABLE T2;
7) Drop VIEW V;
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