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# Calculations between two rows in one table

I am trying to generate a report that calculates the difference between the number of visits and page views when...

pull_id=1 from when pull_id=2. The problem I am having is that I am only using one table and not joining to another table. In other words, how do I distinguish the page views and visits to make the subtraction?

```CREATE TABLE INSIGHT_STATS(
INSIGHT_STATS_ID    NUMBER(28) NOT NULL,
NUM_OF_VISITS       NUMBER(6),
NUM_OF_PAGE_VIEWS   NUMBER(6),
LAST_SEEN_DATE      DATE,
FIRST_SEEN_DATE     DATE,
VISIT_START_DTIME   DATE,
OMEDA_USER_ID       VARCHAR2(28),
PULL_ID             NUMBER(3)
);```

Even though you are dealing with only one table, what you have to do in the query is imagine that there are two copies of it. This is called a self-join.

```select t1.INSIGHT_STATS
, t2.(NUM_OF_VISITS) -
t1.(NUM_OF_VISITS) as DiffVisits
, t2.(NUM_OF_PAGE_VIEWS) -
t1.(NUM_OF_PAGE_VIEWS) as DiffPageviews
from INSIGHT_STATS t1
inner
join INSIGHT_STATS t2
on t1.INSIGHT_STATS_ID
= t2.INSIGHT_STATS_ID
where t1.PULL_ID = 1
and t2.PULL_ID = 2```

Notice that there's a join condition which matches values of INSIGHT_STATS_ID, which I assume is part of the primary key of this table. In other words, a single INSIGHT_STATS_ID value is in the table multiple times, each with a different PULL_ID value. If that's not the case, you should be able to modify the query accordingly. The important point is the all rows within the same INSIGHT_STATS_ID value are combined into all combinations of PULL_ID values, but the WHERE clause selects only the specific match out of all combinations.

Also, notice that the differences are calculated by subtracting PULL_ID=1 values from PULL_ID=2, assuming that PULL_ID=2 is later.

This was last published in January 2004

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i want to find the day difference between second row of same column and first row of same column and third row of same column and second row of same column and so on... any body please help me to fix this.
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