Only 1 row in recordset but all rows in table get updated - vb6

Question

The query retrieves a single record as is confirmed by the recordcount but every single row in the table gets updated
I am using vb6 and ms ado 2.8
The Firebird version is 2.5.4.26856 (x64).
Firebird ODBC driver 2.0.3.154
The computer is windows 7 home edition 64 bit
Dim cn As New ADODB.Connection
Dim rs As New ADODB.Recordset
Dim cs As String
Dim dbPath As String
dbPath = "c:\Parkes\Parkes.fdb"
cs = "DRIVER={Firebird/Interbase(r) Driver}; DBNAME=localhost:" & dbPath & "; UID=SYSDBA; PWD=masterkey;"
cn.ConnectionString = cs
cn.Open
Dim sQuery As String
sQuery = "select memo from clients where clientID = 10021 "
rs.Open sQuery, cn, adOpenStatic, adLockOptimistic
If rs.BOF <> True Or rs.EOF <> True Then
'putting msgbox rs.recordcount here confirms only 1 record in recordset
rs.Movefirst
rs.Fields("memo") = "blah"
rs.Update
End If
Set rs = Nothing
Set cn = Nothing
If I alter the query slightly by also selecting a second column, the client surname then only rows with the same value in the surname column as that of of the row where the clientid is 10021 get edited.
sQuery = "select memo, surname from clients where clientID = 10021 "
I cannot understand how more than one row should be edited when the recordset contains only a single row
EDIT: Having read around the web a bit this is my understanding of what is happening.
It seems that the update method identifies which records to update based on the selected columns in the recordset.
So if you select fields a,b,c,d and are updating field a, it will only update records in the database whose values for a,b,c,d match those in the recordset.
The best way to ensure that you only update a single record is to include the primary key in the selected fields.
So if I had written my query as in the line below, only a single record would have been updated because the clientID column contains unique values.
sQuery = "select memo, clientID from clients where clientID = 10021 "
It makes sense thinking about it but the way I wrote the query originally seems to work fine, in my experience, with other databases or am I wrong?

Answer 1

I tested your code everything was fine and only update one row. I only want to suggest you a simple way to check whether record exist or not. that could be like this:
if rs.rows.count > 0 then
' no need to move recordset to first by default its on the first row
end if