Embedded SQL query in C - variable not in select list

Question

Hello everyone,
I am new to using embedded SQL in C. I have written a query based on some very similar code I have found and I keep getting this error:
ID: ORA-XXXX
OVRD:
TEXT: Oracle Errors Found - Consult Application Development Team
INFO:
SQLC: -1007
GLM: ORA-01007: variable not in select list
If anyone could help me figure out what I am doing wrong that is causing this error it would be much appreciated. Thanks in advance!
Here is the query that is generating the error, I have changed the variable names but the syntax is the same:
SELECT TEMP_TABLE.tble,
TEMP_TABLE.item_date,
TEMP_TABLE.item_number,
TEMP_TABLE.item_id,
TEMP_TABLE.amount,
TEMP_TABLE.method
FROM (
SELECT 'C' tble,
item_date,
item_number,
item_id,
amount,
method
FROM current
WHERE (settlement_date IS NULL)
UNION ALL
SELECT '1' tble,
item_date,
item_number,
item_id,
amount,
method
FROM prev1
WHERE (date IS NULL)
UNION ALL
SELECT '2' tble,
item_date,
item_number,
item_id,
amount,
pay_method
FROM prev2
WHERE (date IS NULL)
UNION ALL
SELECT '3' tble,
item_date,
item_number,
item_id,
amount,
pay_method
FROM prev3
WHERE (date IS NULL)
UNION ALL
SELECT '4' tble,
item_date,
item_number,
item_id,
amount,
method
FROM prev4
WHERE (date IS NULL)) TEMP_TABLE
WHERE (TEMP_TABLE.item_date,
TEMP_TABLE.item_number,
TEMP_TABLE.item_id) IN
(SELECT item_date, item_number, item_id
FROM item
WHERE (source, location) IN
(SELECT source, location
FROM SOURCE_REF
WHERE online = 'O'
AND (source, location) IN
(SELECT source,
location
FROM SOURCE_METHOD_REF
WHERE type = 'P')))

Answer 1

Oh yeah I forgot to add that I have tested the query in TOAD and it works just fine so its something to do with embedding it into C I believe.