How to link two unrelated tables, through one table with common values? - sql

Question

I am adding a commission percent column to an existing query. However, the commission data sits in a table unrelated to the main table (A) used within the query. However, these two tables have common columns/values with Table B.
I have three tables, A, B and C below
Table A
Reference Value_Name Renewal_Code
1 A N
2 A R
3 B N
4 A R
4 A N
Table B
Reference Value_Name Prod_Code
1 A 0016
2 A 0027
4 A 0032
4 A 0032
Table C
A_Prod_Code A_Tans_Code **Commission_Percent**
0016 Renewal 5
0027 Renewal 5
0032 New 10
0032 Renewal 5
I need to get the Commission_Percent from Table C relating to the corresponding Renewal_Code from Table A. This is the same as A_Tans_Code from Table C except that Table C spells out Renewal or New and Table A only uses R or N.
I have been able to pull through the Commission_Percent column into the output by using Table B for common values, but all values show as NULL.
I have also tried using a decode statement in order to link the Renewal_code/A_Trans_Code columns from Tables A and C.
(
SELECT
distinct c.commision_percent
FROM
TableA a
JOIN TableB b ON a.reference = b.reference
AND b.value_name = 'A'
JOIN TableC c ON b.prod_code = c.a_prod_code
AND b.value_name = 'A'
JOIN TableC c ON a.renewal_code = decode(c.a_trans_code, 'Rewnal','R','New','N')
) Commission_Percent
I need the correct commission_percent for Renewal and New business to come through for each reference. So far, I am only getting NULLs as I am having a hard time linking Tables A and C's Renewal_code and A_prod_code columns.
Any help is greatly appreciated!

Answer 1

This creates reproducible testing by cleaning up temp tables and re-inserting the data.
And could be a model for other solutions.
The SQL 'Select...' joins to a single TableC that has two parts to the ON condition-- prod_code and renewal_code (instead of two joins). Just remove the "a.*," to use it in your sql. (the decode function was changed to use a subscript of the first char of the A_Trans_Code).
IF OBJECT_ID('tempdb..#TableA') IS NOT NULL DROP TABLE #TableA
GO
CREATE TABLE #TableA
( Reference INTEGER
, Value_Name VARCHAR(10)
, Renewal_Code VARCHAR(10) )
INSERT INTO #TableA VALUES( 1, 'A', 'N' );
INSERT INTO #TableA VALUES( 2, 'A', 'R' );
INSERT INTO #TableA VALUES( 3, 'B', 'N' );
INSERT INTO #TableA VALUES( 4, 'A', 'R' );
INSERT INTO #TableA VALUES( 4, 'A', 'N' );
IF OBJECT_ID('tempdb..#TableB') IS NOT NULL DROP TABLE #TableB
GO
CREATE TABLE #TableB
( Reference INTEGER
, Value_Name VARCHAR(10)
, Prod_Code VARCHAR(10) )
INSERT INTO #TableB VALUES( 1, 'A', '0016' );
INSERT INTO #TableB VALUES( 2, 'A', '0027' );
INSERT INTO #TableB VALUES( 4, 'A', '0032' );
INSERT INTO #TableB VALUES( 4, 'A', '0032' );
IF OBJECT_ID('tempdb..#TableC') IS NOT NULL DROP TABLE #TableC
GO
CREATE TABLE #TableC
( Prod_Code VARCHAR(10)
, A_Trans_Code VARCHAR(10)
, Commission_Percent INTEGER )
INSERT INTO #TableC VALUES( '0016', 'Renewal', 5 );
INSERT INTO #TableC VALUES( '0027', 'Renewal', 5 );
INSERT INTO #TableC VALUES( '0032', 'New', 10 );
INSERT INTO #TableC VALUES( '0032', 'Renewal', 5 );
SELECT distinct a.*, c.commission_percent
FROM #TableA a
JOIN #TableB b ON a.reference = b.reference
AND a.value_name = b.value_name
JOIN #TableC c ON b.prod_code = c.prod_code
AND a.renewal_code = SUBSTRING(c.a_trans_code,1,1)
Results are--
Reference Value_Name Renewal_Code commission_percent
2 A R 5
4 A N 10
4 A R 5
Code to put in your sql
( SELECT distinct c.commission_percent
FROM TableA a
JOIN TableB b ON a.reference = b.reference
AND a.value_name = b.value_name
JOIN TableC c ON b.prod_code = c.prod_code
AND a.renewal_code = SUBSTRING(c.a_trans_code,1,1)
) Commission_Percent

Answer 2

WITH table_a AS (
SELECT 1 AS reference, 'A' AS value_name, 'N' AS renewal_code FROM DUAL UNION ALL
SELECT 2 AS reference, 'A' AS value_name, 'R' AS renewal_code FROM DUAL UNION ALL
SELECT 3 AS reference, 'B' AS value_name, 'N' AS renewal_code FROM DUAL UNION ALL
SELECT 4 AS reference, 'A' AS value_name, 'R' AS renewal_code FROM DUAL UNION ALL
SELECT 4 AS reference, 'A' AS value_name, 'N' AS renewal_code FROM DUAL
),
table_b AS (
SELECT 1 AS reference, 'A' AS value_name, '0016' AS prod_code FROM DUAL UNION ALL
SELECT 2 AS reference, 'A' AS value_name, '0027' AS prod_code FROM DUAL UNION ALL
/* SELECT 4 AS reference, 'A' AS value_name, '0032' AS prod_code FROM DUAL UNION ALL duplicate row excluded */
SELECT 4 AS reference, 'A' AS value_name, '0032' AS prod_code FROM DUAL
),
table_c AS (
SELECT '0016' AS a_prod_code, 'Renewal' AS a_tans_code, 5 AS commission_percent FROM DUAL UNION ALL
SELECT '0027' AS a_prod_code, 'Renewal' AS a_tans_code, 5 AS commission_percent FROM DUAL UNION ALL
SELECT '0032' AS a_prod_code, 'New' AS a_tans_code, 10 AS commission_percent FROM DUAL UNION ALL
SELECT '0032' AS a_prod_code, 'Renewal' AS a_tans_code, 5 AS commission_percent FROM DUAL
)
SELECT a.reference AS ref_a,
a.value_name AS value_name_a,
b.reference AS ref_b,
b.value_name AS value_name_b,
a.renewal_code,
b.prod_code,
c.commission_percent
FROM table_a a
LEFT OUTER JOIN table_b b
ON a.value_name = b.value_name
AND a.reference = b.reference
LEFT OUTER JOIN table_c c
ON SUBSTR(c.a_tans_code, 1, 1) = a.renewal_code
AND c.a_prod_code = b.prod_code
;
The common table expression (CTE) is just to create the same values you posted (CTE is the part using the WITH construct).
Results:
REF_A VALUE_NAME_A REF_B VALUE_NAME_B RENEWAL_CODE PROD_CODE COMMISSION_PERCENT
---------- --------------- ---------- --------------- --------------- ---------- --------------------
2 A 2 A R 0027 5
4 A 4 A N 0032 10
4 A 4 A R 0032 5
1 A 1 A N 0016
3 B N
You may have to check the values in the rows you posted that do not result in a join. This also assumes there are no codes:code_name relationships that violate the rule of first letter of code name = code.