Writing SQL statement to select from multiple rows - sql

Question

This might be a silly question to ask. I will appreciate any kind of help.
I'm trying to write a query that count the number of rows based on the logic as below:
count no rows where username = #username and friendsname = #friendsname and username = #friendsname and #friendsname = #username where status = 0
consider the table in the diagram below:
The query should return 1 since id '18' and id '20' have reciprocal values. How will this query be written?
I have written the query as follows which doesn't work:
bool flag = false;
StringBuilder query = new StringBuilder();
query.Append("SELECT Count(id) from friends where username=#username AND friend_username=#friend_username AND username = #friend_username AND friend_username = #username");
query.Append(" AND status=0");
using (SqlConnection con = new SqlConnection(Config.ConnectionString))
{
con.Open();
using (SqlCommand cmd = new SqlCommand(query.ToString(), con))
{
cmd.CommandType = CommandType.Text;
cmd.Parameters.Add(new SqlParameter("#username", username));
cmd.Parameters.Add(new SqlParameter("#friend_username", friendusername));
if (Convert.ToInt32(cmd.ExecuteScalar()) > 0)
flag = true;
}
}
return flag;

Answer 1

If I'm not mistaken you're trying to count rows given a specific #username and #friendusername that have reciprocal values based on your conditions.
Below query should help, though - I have not tested it in action!
SELECT COUNT(*) as reciprocal_values_no
FROM table_name tbl1
WHERE
username = #username
AND friend_username = #friendusername
AND status = 0
AND EXISTS (
SELECT 1 FROM table_name tbl2 WHERE tbl1.username = tbl2.friend_username AND tbl1.friend_username = tbl2.username )

Answer 2

try this
select username,friend_username,status, count(*)
from table_name
group by username,friend_username,status
having count(*) > 1