oracle sql row count affected by select clause

Question

While working on a oracle SQL , noticed that adding a column to the selected columns increases the total rows in the result. The query is using multiple subqueries declared using WITH. The join in the final query is a left join. Why is the row count getting impacted?

Are you using the distinct keyword?

Dan Bracuk
– Dan Bracuk

2017-07-04 18:59:53 +00:00
Commented Jul 4, 2017 at 18:59 — Dan Bracuk
– Dan Bracuk, Commented Jul 4, 2017 at 18:59
yes. the select has a distinct keyword.

Prakash
– Prakash

2017-07-04 19:00:42 +00:00
Commented Jul 4, 2017 at 19:00 — Prakash
– Prakash, Commented Jul 4, 2017 at 19:00

Thorsten Kettner · Accepted Answer · 2017-07-04 19:01:19Z

The only way I can think of to increase the number of result rows by adding a column to the SELECT clause is when using SELECT DISTINCT.

SELECT DISTINCT removes duplicates from the results, so

 col1 col2 a b a b a c a c

becomes

 col1 col2 a b a c

When adding a column

 col1 col2 col3 a b d a b e a c f a c f

becomes

 col1 col2 col3 a b d a b e a c f

for instance, which is one row more than before.

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