Jmeter Issues with JDBC Request and variables

I'm having a few issues with Jmeter and storing/using variables from them:

1. I have a JDBC request which does a VERY simple "select statement" with the following sql:

   select count(member_id) from member
   

This is then stored in a variable named count. I know what the count should be (should be 312), but the value count_1 gets is 40077. What is even more troubling is at some point, it started working and getting the correct count. Any idea what is going on?

1. In a seperate JDBC request, I retrieve a list of members:

   select member_id from members 
   

This is stored in开发者_如何学Go a variable named members. Then I created a THIRD JDBC request to query and grab a random member:

select * from members where member_id = ? 

In "Parameter values", I put in ${__V(member_${__Random(1,10)})} (note I put 10, not $count because I can't even get it to work correctly with a hard coded number). I see that this gets parsed correctly, but the error I get is:

org.postgresql.util.PSQLException: ERROR: invalid input syntax for integer: "member_7" 

So it's not substituting the member_7 variable's value. Instead it's just passing the string. What am I doing wrong here?

---

If you have table member, where you have some member_id in this way (for example):

| member_id |
+-----------+
| 1         |
| 2         |
| 1         |

And you would like to count UNIQUE members from this table, you must use SELECT in this way:

SELECT COUNT(DISTINCT member_id) FROM member;

When you miss keyword DISTINCT, you will get only a COUNT of lines in the table.

The second SELECT you have to use in similar way:

SELECT DISTINCT member_id FROM member;

And the last question is, why you tried to integer value assign a value like 'member_7'?