Difference in results of queries on same data

Question

Hi all
I have two tables, FURNITURE which contains transactions information of the customers who come for shoping to a store. IDNO column in the table shows ID of the customer, RECEIPTNO shows the receipt number of the customer. Each single visit will depict a single visit by any customer. D_CUSTOMER table contains customers information and demographics information. A single customer IDNO may have multiple entries in D_CUSTOMER table because a single customer may have multiple membership cards and hence multiple entries in D_CUSTOMER table.
Now I want to know unique customers show did shoping during a time period and also their number of visits. So I am using following query to do this.
select  COUNT(DISTINCT IDNO) AS UNIQ, COUNT(distinct RECEIPTNO) AS VISIT
from FURNITURE
where trandate_period_skey between 946 and 1126
UNIQ         VISIT
148269       265907
Here we see that there are total 148269 distinct customer who visited total 265907 times for shoping of furniture. Each distinct receiptno shows a single visit.
In my second query I simply involving D_CUSTOMER table to find out that how many visits were males and how many were females
select GENDER, COUNT(DISTINCT A.IDNO),COUNT(distinct RECEIPTNO) AS VISIT
from FURNITURE A,
(SELECT IDNO, MAX(GENDER) AS GENDER FROM D_CUSTOMER WHERE MEMBERTYPE = 'PA' GROUP BY IDNO) b
where TRANDATE_PERIOD_SKEY between 946 and 1126
and a.IDNO = b.IDNO
group by gender
GENDER     UNIQ    VISIT
F 103876 188573
M 44393 77357
Now here comes the problem. If we sum values under UNIQ column, total is 148269 (103876 Females and 44393 Males), which is same as the value in the result of first query. But, if we sum the values under VISIT column, 188573 visits by Females and 77357 visits by Males and total is 265930 which is different from the value of COUNT(DISTINCT RECEIPT) in first query because first query says total visits are 265907.
I can't understand why I am seeing this difference. In my second query, the sum of values under VISIT column should be 265907
Any one who can point out where are things going wrong and why there is difference in result?
Salman

Answer 1

Thanks rp0428. Actually first table already have data based on member with membertype='PA'.
Any way, I have got the solution. Actually I had same receipt number issued to two different customers, one make and one female and hence while grouping, this type of receipts were being counted for both genders and hence total was greater during grouping.
Case is closed.
Salman