Unable to convert this legacy SQL into Standard SQL in Google BigQuery - google-bigquery

Question

I am not able to validate this legacy sql into standard bigquery sql as I don't know what else is required to change here(This query fails during validation if I choose standard SQL as big query dialect):
SELECT
lineitem.*,
proposal_lineitem.*,
porder.*,
company.*,
product.*,
proposal.*,
trafficker.name,
salesperson.name,
rate_card.*
FROM (
SELECT
*
FROM
dfp_data.dfp_order_lineitem
WHERE
DATE(end_datetime) >= DATE(DATE_ADD(CURRENT_TIMESTAMP(), -1, 'YEAR'))
OR end_datetime IS NULL ) lineitem
JOIN (
SELECT
*
FROM
dfp_data.dfp_order) porder
ON
lineitem.order_id = porder.id
LEFT JOIN (
SELECT
*
FROM
adpoint_data.dfp_proposal_lineitem) proposal_lineitem
ON
lineitem.id = proposal_lineitem.dfp_lineitem_id
JOIN (
SELECT
*
FROM
dfp_data.dfp_company) company
ON
porder.advertiser_id = company.id
LEFT JOIN (
SELECT
*
FROM
adpoint_data.dfp_product) product
ON
proposal_lineitem.product_id=product.id
LEFT JOIN (
SELECT
*
FROM
adpoint_data.dfp_proposal) proposal
ON
proposal_lineitem.proposal_id=proposal.id
LEFT JOIN (
SELECT
*
FROM
adpoint_data.dfp_rate_card) rate_card
ON
proposal_lineitem.ratecard_id=rate_card.id
LEFT JOIN (
SELECT
id,
name
FROM
dfp_data.dfp_user) trafficker
ON
porder.trafficker_id =trafficker.id
LEFT JOIN (
SELECT
id,
name
FROM
dfp_data.dfp_user) salesperson
ON
porder. salesperson_id =salesperson.id

Answer 1

Most likely the error you are getting is something like below
Duplicate column names in the result are not supported. Found duplicate(s): name
Legacy SQL adjust trafficker.name and salesperson.name in your SELECT statement into respectively trafficker_name and salesperson_name thus effectively eliminating column names duplication
Standard SQL behaves differently and treat both those columns as named name thus producing duplication case. To avoid it - you just need to provide aliases as in example below
SELECT
lineitem.*,
proposal_lineitem.*,
porder.*,
company.*,
product.*,
proposal.*,
trafficker.name AS trafficker_name,
salesperson.name AS salesperson_name,
rate_card.*
FROM ( ...
You can easily check above explained using below simplified/dummy queries
#legacySQL
SELECT
porder.*,
trafficker.name,
salesperson.name
FROM (
SELECT 1 order_id, 'abc' order_name, 1 trafficker_id, 2 salesperson_id
) porder
LEFT JOIN (SELECT 1 id, 'trafficker' name) trafficker
ON porder.trafficker_id =trafficker.id
LEFT JOIN (SELECT 2 id, 'salesperson' name ) salesperson
ON porder. salesperson_id =salesperson.id
and
#standardSQL
SELECT
porder.*,
trafficker.name AS trafficker_name,
salesperson.name AS salesperson_name
FROM (
SELECT 1 order_id, 'abc' order_name, 1 trafficker_id, 2 salesperson_id
) porder
LEFT JOIN (SELECT 1 id, 'trafficker' name) trafficker
ON porder.trafficker_id =trafficker.id
LEFT JOIN (SELECT 2 id, 'salesperson' name ) salesperson
ON porder. salesperson_id =salesperson.id
Note: if you have more duplicate names - you need to alias all of them too