{"id":3115,"date":"2024-09-30T22:45:31","date_gmt":"2024-10-01T03:45:31","guid":{"rendered":"https:\/\/www.dpriver.com\/blog\/?p=3115"},"modified":"2024-10-06T02:33:44","modified_gmt":"2024-10-06T07:33:44","slug":"mastering-nested-sub-queries-accurate-table-column-relationships-in-complex-sql-with-star-columns","status":"publish","type":"post","link":"https:\/\/www.dpriver.com\/blog\/2024\/09\/mastering-nested-sub-queries-accurate-table-column-relationships-in-complex-sql-with-star-columns\/","title":{"rendered":"Mastering Nested Sub-Queries: Accurate Table-Column Relationships in Complex SQL with Star Columns"},"content":{"rendered":"\n
This article discusses the challenge of building correct relationships between tables and columns in nested sub-queries with star columns. It uses a Teradata SQL code example to illustrate the process.<\/p>\n\n\n\n
The article focuses on a sub-query aliased as SUBSCRIBER_ and its derived columns, which are used in an outer query. It explains that some columns are explicitly listed in the sub-query’s select list, while others come from a star column (SUBSCR.*) referencing the PRD2_ODW.SUBSCRIBER_ table.<\/p>\n\n\n\n
The analysis then examines the outer query’s select list, particularly columns from the SUBSCRIBER_ sub-query. It demonstrates how to determine the origin of each column:<\/p>\n\n\n\n
\n
Columns not explicitly listed in the sub-query (e.g., SUBS_ID, ACTIVATION_DATE) are derived from the star column and belong to the PRD2_ODW.SUBSCRIBER_ table.<\/li>\n\n\n\n
Columns explicitly listed in the sub-query (e.g., FIRST_TP_ID, CUST_ID) are traced back to their original tables (SUBS_CUST in these cases).<\/li>\n<\/ol>\n\n\n\n
This process helps in accurately mapping columns to their source tables, which is crucial for understanding complex queries and maintaining data lineage in nested sub-queries with star columns.<\/p>\n\n\n\n
Here is the Teradata SQL code used in the demo:<\/p>\n\n\n\n<\/figure>\n\n\n\n
In line 130:<\/strong> SUBSCRIBER_ is the alias of the sub-query, and derived column of this sub-query is used in the outer query.<\/p>\n\n\n\n
The derived column for SUBSCRIBER_ is start from line 90 to line 111 that from different tables. There is also a star column * prefixed with SUBSCR which is the alias of the PRD2_ODW.SUBSCRIBER_ table.<\/p>\n\n\n\n
Now, let take a look at the outer query, especially the select list part that start from line 23 to line 87, and we only focus on the columns that from the sub-query SUBSCRIBER_.<\/p>\n\n\n\n<\/figure>\n\n\n\n
line 23<\/strong>: SUBSCRIBER_.SUBS_ID, column SUBS_ID is not explicitly listed in the select list from line 90 to line 111, so this column must from SUBSCR.*, and SUBSCR is the alias of the PRD2_ODW.SUBSCRIBER_ table in line 112.<\/p>\n\n\n\n
\n
Conclusion: SUBS_ID is the column of table: PRD2_ODW.SUBSCRIBER_<\/li>\n<\/ul>\n\n\n\n
line 25: <\/strong>SUBSCRIBER_.REGISTRATION_DATE (NAMED REGISTRATION_DTTM), column REGISTRATION_DATE is not explicitly listed in the select list from line 90 to line 111, so this column must from SUBSCR.*, and SUBSCR is the alias of the PRD2_ODW.SUBSCRIBER_ table.<\/p>\n\n\n\n
\n
Conclusion: REGISTRATION_DATE is the column of table: PRD2_ODW.SUBSCRIBER_<\/li>\n<\/ul>\n\n\n\n
line 26:<\/strong> SUBSCRIBER_.FIRST_CALL (NAMED FIRST_CALL_DTTM), column FIRST_CALL is not explicitly listed in the select list from line 90 to line 111, so this column must from SUBSCR.*, and SUBSCR is the alias of the PRD2_ODW.SUBSCRIBER_ table.<\/p>\n\n\n\n
\n
Conclusion: FIRST_CALL is the column of table: PRD2_ODW.SUBSCRIBER_<\/li>\n<\/ul>\n\n\n\n
line 27:<\/strong> SUBSCRIBER_.FIRST_TP_ID, column FIRST_TP_ID is explicitly listed in the select list at line 91: SUBS_CUST.FIRST_TP_ID.<\/p>\n\n\n\n
\n
Conclusion: FIRST_TP_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 28:<\/strong> SUBSCRIBER_.CUST_ID, column CUST_ID is explicitly listed in the select list at line 92: SUBS_CUST.CUST_ID.<\/p>\n\n\n\n
\n
Conclusion: CUST_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 30:<\/strong> SUBSCRIBER_.DEALER_ID, column DEALER_ID is explicitly listed in the select list at line 102: SUBS_CUST.DEALER_ID.<\/p>\n\n\n\n
\n
Conclusion: DEALER_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 35: <\/strong> SUBSCRIBER_.SRVP_COV_CUST_ID, column SRVP_COV_CUST_ID is explicitly listed in the select list at line 93: SUBS_CUST.SRVP_COV_CUST_ID.<\/p>\n\n\n\n
\n
Conclusion: SRVP_COV_CUST_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 37<\/strong>: SUBSCRIBER_.TP_ID, column TP_ID is explicitly listed in the select list at line 94: SUBS_CUST.TP_ID.<\/p>\n\n\n\n
\n
Conclusion: TP_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 38:<\/strong> SUBSCRIBER_.BLOCK_QUOTA (NAMED IS_BLOCK_QUOTA), column BLOCK_QUOTA is explicitly listed in the select list at line 95: SUBS_CUST.BLOCK_QUOTA.<\/p>\n\n\n\n
\n
Conclusion: BLOCK_QUOTA is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 40:<\/strong> WHEN (SUBSCRIBER_.REL_CAT_ID < 0) THEN (NULL), column REL_CAT_ID is explicitly listed in the select list at line 96: SUBS_CUST.REL_CAT_ID.<\/p>\n\n\n\n
\n
Conclusion: REL_CAT_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 47:<\/strong> SUBSCRIBER_.STATUS_CHNG_RSN_ID, column STATUS_CHNG_RSN_ID is explicitly listed in the select list at line 97: SUBS_CUST.STATUS_CHNG_RSN_ID.<\/p>\n\n\n\n
Conclusion: <\/strong>STATUS_CHNG_RSN_ID is the column of table: SUBS_CUST<\/p>\n\n\n\n
line 48:<\/strong> SUBSCRIBER_.STATUS_ID, column STATUS_ID is explicitly listed in the select list at line 98: SUBS_CUST.STATUS_ID.<\/p>\n\n\n\n
\n
Conclusion: <\/strong> STATUS_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 49:<\/strong> SUBSCRIBER_.SUBS_TYPE_ID, column SUBS_TYPE_ID is explicitly listed in the select list at line 99: SUBS_CUST.SUBS_TYPE_ID,<\/p>\n\n\n\n
\n
Conclusion: SUBS_TYPE_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 50:<\/strong> SUBSCRIBER_.BRANCH_ID (NAMED BRANCH_ID), column BRANCH_ID is explicitly listed in the select list at line 100: SUBS_CUST.BRANCH_ID,<\/p>\n\n\n\n
\n
Conclusion: BRANCH_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 61:<\/strong> SUBSCRIBER_.BRANCH_ID (NAMED BRANCH_ID), column BRANCH_ID is explicitly listed in the select list at line 100: SUBS_CUST.BRANCH_ID,<\/p>\n\n\n\n
\n
Conclusion: BRANCH_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 62:<\/strong> CAST((SUBSCRIBER_.CALC_PLATFORM_ID) AS DECIMAL(2, 0))(NAMED CALC_PLATFORM_ID), column CALC_PLATFORM_ID is explicitly listed in the select list at line 110: END)(NAMED CALC_PLATFORM_ID), and this is a column alias, the underlying column is SUBS_CUST.CALC_PLATFORM_ID<\/p>\n\n\n\n
\n
Conclusion: CALC_PLATFORM_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 66:<\/strong> WHEN (((SUBSCRIBER_.BRANCH_ID = 61) AND (SUBSCRIBER_.CALC_PLATFORM_ID IN (6, 7, 8, 9))) AND (:_spVV0 >= DATE ‘2018-04-30’)) THEN (0), column BRANCH_ID is explicitly listed in the select list at line 100: SUBS_CUST.BRANCH_ID,<\/p>\n\n\n\n
\n
Conclusion: BRANCH_ID is the column of table: SUBS_CUST<\/li>\n<\/ul>\n\n\n\n
line 71:<\/strong> CAST((SUBSCRIBER_.LAST_FLASH_DTTM) AS DATE)(NAMED LAST_FLASH_DTTM), column LAST_FLASH_DTTM is explicitly listed in the select list at line 104: SUBS_CLR_FLASH.LAST_FLASH_DTTM,<\/p>\n\n\n\n
\n
Conclusion: LAST_FLASH_DTTM is the column of table: SUBS_CLR_FLASH<\/li>\n<\/ul>\n\n\n\n
line 73:<\/strong> WHEN (NOT (SUBSCRIBER_.FLASH_CODE_ID IS NULL)) THEN (SUBSCRIBER_.FLASH_CODE_ID), column FLASH_CODE_ID is explicitly listed in the select list at line 105: SUBS_CLR_FLASH.FLASH_CODE_ID,<\/p>\n\n\n\n
\n
Conclusion: FLASH_CODE_ID is the column of table: SUBS_CLR_FLASH<\/li>\n<\/ul>\n\n\n\n
line 77:<\/strong> WHEN (NOT (SUBSCRIBER_.IF_NEW_CHURN IS NULL)) THEN (SUBSCRIBER_.IF_NEW_CHURN), column IF_NEW_CHURN is explicitly listed in the select list at line 106: SUBS_CLR_FLASH.IF_NEW_CHURN,<\/p>\n\n\n\n
\n
Conclusion: IF_NEW_CHURN is the column of table: SUBS_CLR_FLASH<\/li>\n<\/ul>\n\n\n\n
Conclusion<\/h4>\n\n\n\n
The table PRD2_ODW.SUBSCRIBER_ has the following columns:<\/p>\n\n\n\n
This article discusses the challenge of building correct relationships between tables and columns in nested sub-queries with star columns. It uses a Teradata SQL code example to illustrate the process. The article focuses on a sub-query aliased as SUBSCRIBER_ and its derived columns, which are used in an outer query. It explains that some columns are explicitly listed in the sub-query’s select list, while others come from a star column (SUBSCR.*) referencing the PRD2_ODW.SUBSCRIBER_ table. The analysis then examines the outer query’s select list, particularly columns from the SUBSCRIBER_ sub-query. It demonstrates how to determine the origin of each column:\u2026<\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[1],"tags":[],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":5}},"yoast_head":"\n
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