SQL Query join problem

Question

Hi,
I have two tables in my db, the patient table holds details of patients, the contact table holds details of contacts related to the patient.
patient table
patientid - primary key - int
patient name - varchar
contact table
contactid - primary key - int
patientid - foreign key from patient table - int
incontact - foreign key from paient table to relate contacts - int
My contact table has the following data:
contactid patientid incontact
2              19           21
2               19          22
I can retrieve data for the patients that have been in contact with patientid 19, by using the following join:
SELECT * FROM PATIENT
LEFT JOIN incontact
ON incontact.incontact = patient.patientid
WHERE incontact.patientid = 19
However, can you please tell me how I can get data from the patients table where the incontact is 21?
So I can get contacts from patients and patients from contacts?
Thankyou

Answer 1

Thanks very much for your replies again.
Basically, I have a table of patients, and I would like to link them to each other, many to many.
I populate the incontact table, which stores the original posted patientID, and the new generated patientID. I populate the DB with the code below.
<cfquery name="update" datasource="staffdirectory">
SET NOCOUNT ON
INSERT INTO patient (title,firstname,surname,gender,DOB,telephone,address1,address2,address3,town,postcode
VALUES ('#title#','#firstname#','#surname#','#gender#',#createodbcdate(createdate(startyear, startmonth, startday))#    ,'#telephone#','#address1#','#address2#','#address3#','#town#','#postcode#
SELECT @@Identity AS newid   
SET NOCOUNT OFF
</cfquery>
      <cfquery name="insert" datasource="staffdirectory">
  INSERT INTO incontact (related,incontact)
VALUES (#patientid#,#update.newid#)
</cfquery>
This works fine and I can get all related patients by usingthe following query:
SELECT * FROM patient
LEFT JOIN incontact
ON patient.patientid  = incontact.related
WHERE  incontact.incontact = #patientid#
MY problem occurs when I want to find related patients from the related column, the reverse relationship. I use this seperate query:
SELECT * FROM patient
LEFT JOIN incontact
ON patient.patientid  = incontact.incontact
WHERE  incontact.related= #patientid#
Is there a way I can combine both queries, or is there a better way I can achieve the same result?
Many thanks again