How to test the following SQL script in Oracle 11g - sql

Question

Below is a script written in Oracle 11g:
MERGE INTO tblbio t
USING (SELECT e.id, tblduplicate.cpid, e.bdt,e.LN, e.FN
FROM tblduplicate, entities where
trim(e.id) = trim(tblduplicate.id)) source
ON (t.cpid = source.cpid and trim(t.bdt) = trim(source.bdt))
WHEN MATCHED
THEN
UPDATE SET t.id = source.id, t.stat = '4'
WHERE t.cmp = 'HHCC'
AND t.thn = '2013'
AND trim(lower(source.LN)) = trim(lower(t.LN))
AND trim(lower(source.FN)) = trim(lower(t.FN))
AND nvl(trim(t.bdt), ' ') <> ' '
AND t.bdt <> '00000000'
AND nvl(trim(source.bdt), ' ') <> ' '
and source.bdt <> '00000000'
AND t.stat <> '4'
Due to my data integrity problem, this script once in awhile will generate more than 1 records. In which this script will generate error.
I want to create validation prior this script is run. When my validation generate more than 1 records I stop this script from running. How can I do that?
I tried to write the following for my validation to capture record count but Oracle just did not like it.
select* from tblbio t <-----
USING (SELECT e.id, tblduplicate.cpid, e.bdt,e.LN, e.FN
FROM tblduplicate, entities where
trim(e.id) = trim(tblduplicate.id)) source
ON (t.cpid = source.cpid and trim(t.bdt) = trim(source.bdt))
WHEN MATCHED
THEN
select * from tblbio t <-----
WHERE t.cmp = 'HHCC'
AND t.thn = '2013'
AND trim(lower(source.LN)) = trim(lower(t.LN))
AND trim(lower(source.FN)) = trim(lower(t.FN))
AND nvl(trim(t.bdt), ' ') <> ' '
AND t.bdt <> '00000000'
AND nvl(trim(source.bdt), ' ') <> ' '
and source.bdt <> '00000000'
AND t.stat <> '4'

Answer 1

Converting original MERGE query to select from tbiblio:
MERGE INTO ... USING --> select from ... join
WHEN MATCHED THEN UPDATE SET ... WHERE --> WHERE
Final query:
select * from tblbio t
JOIN (SELECT e.id, tblduplicate.cpid, e.bdt,e.LN, e.FN
FROM tblduplicate, entities where
trim(e.id) = trim(tblduplicate.id)) source
ON (t.cpid = source.cpid and trim(t.bdt) = trim(source.bdt))
WHERE t.cmp = 'HHCC'
AND t.thn = '2013'
AND trim(lower(source.LN)) = trim(lower(t.LN))
AND trim(lower(source.FN)) = trim(lower(t.FN))
AND nvl(trim(t.bdt), ' ') <> ' '
AND t.bdt <> '00000000'
AND nvl(trim(source.bdt), ' ') <> ' '
and source.bdt <> '00000000'
AND t.stat <> '4'