Column ambigously defined in subquery with join on another subquery - sql

Question

I keep getting a column ambiguously defined error when joining two sub queries. However I have defined all my columns properly. I want to get all the data from the first query and add some data to it where available. How can this be fixed?
SELECT
sq2.month,
sq1.PRIMARY_MER_NUM ,
sq1.PRIMARY_EXT_MID ,
sq1.MER_DBA_NAM,
sq1.CLG_NUM,
sq1.ENT_NUM,
sq1.ENT_NAM,
sq1.MER_OPN_DTE,
sq1.MER_CLS_DTE,
sq1.MER_FST_DPST_DTE,
sq1.CLG_NUM ,
sq1.ENT_NUM,
sq2.gross_volume,
sq2.transaction_count
FROM
(SELECT DISTINCT
PRIMARY_MER_NUM ,
PRIMARY_EXT_MID ,
MER_DBA_NAM,
CLG_NUM,
ENT_NUM,
ENT_NAM,
MER_OPN_DTE,
MER_CLS_DTE,
MER_FST_DPST_DTE,
CLG_NUM ,
ENT_NUM
FROM
bi.t_mer_dim_na
WHERE
CLG_NUM = 7
AND ENT_NUM IN ('45810', '45811', '46849', '45948', '45824',
'46911', '45509', '46845', '48902')
) sq1
LEFT JOIN
(SELECT
TRUNC(BAT_REF_DTE, 'MM') AS month,
MER_NUM,
SUM(bat_prd_trn_dr_amt + bat_prd_trn_cr_amt) AS gross_volume,
SUM(bat_item_num) AS transaction_count
FROM
TDS.BAT_T3
WHERE
1 = 1
AND bat_ref_dte >= TRUNC(sysdate, 'MM')
GROUP BY
TRUNC(BAT_REF_DTE, 'MM'), MER_NUM) SQ2 ON sq1.primary_mer_num = sq2.MER_NUM;

Answer 1

You have CLG_NUM and ENT_NUM selected twice in your first derived table SQL1
FROM (
select DISTINCT
PRIMARY_MER_NUM ,
PRIMARY_EXT_MID ,
MER_DBA_NAM,
CLG_NUM, --1
ENT_NUM, --1
ENT_NAM,
MER_OPN_DTE,
MER_CLS_DTE,
MER_FST_DPST_DTE,
CLG_NUM, --2
ENT_NUM --2
from bi.t_mer_dim_na
That makes selecting sql1.CLG_NUM and sql1.ENT_NUM ambiguous in your outer select (where you also select both twice)