hi please help me in converting this sql server into oracle

UPDATE t1
SET t1.H = 'I'
FROM dbo.ABC AS t1
INNER JOIN (
SELECT DISTINCT MIN(A) AS A
FROM dbo.ABC
GROUP BY C
HAVING COUNT(*) > 1
) AS x ON x.A = t1.A

You might get (more) responses if you provided DDL for tables involved,
DML (INSERT) to populate test data in tables & actual results from SQL against the sample data.
Since I am not a SQL Server person & am not sure EXACTLY what the post SQL does.

It would give us a fighting chance to reproduce what exists now.

Try this:

Table: ABC
A B C D E F G H
50586 152476 Dextromethorphan-Guaifenesin 10-100 mg/5 mL Tussin DM 10 mg-100 mg/5 mL Syrup R
89446 433219 Dextromethorphan-Guaifenesin 10-100 mg/5 mL Tussin DM 10 mg-100 mg/5 mL Syrup A
165511 433219 Dextromethorphan-Guaifenesin 10-100 mg/5 mL Tussin DM 10 mg-100 mg/5 mL Syrup A

i want to update Table ABC COLUMN H as 'I' If all columns matches except A

WHAT IS THE UPDATE QUERY IN DOING SO.

SOMEWHERE TRIED LIKE

UPDATE TABLE ABC SET H='I' WHERE A IN (SELECT MIN(A) FROM ABC GROUP BY C HAVING COUNT(*)>1)

I AM HAVING MORE TAHN 1.5 LAKH RECORDS IN MY TABLE.HOW TO UPDATE IF IT MATCHES ABOVE CRITERIA.....

I would have prefered follwing way to update 1.5 LAKH record
1) Create empty tmp table as source table.
2) Load updated data into tmp table using nolog option.
3) Clean source table.
4) Load updated data from tmp table to source table using nolog option.

Still not sure what you're attempting to do, But try this sql out, it should update all rows where columns(b thru h) are the same on more than one row:

Code:

update abc
  set  h  =  'I'
where  ( b, c, d, e, f, g, h ) in
       ( select b, c, d, e, f, g, h, count(*)
          from  abc
         group by b, c, d, e, f, g, h
         having count(*) > 1 )

Thank you very much