跨表对比Shows列关联Rating值，输出对应较大值的技术需求

To solve this problem—matching shows by their occurrence order (even when names repeat) and identifying which table has the higher associated rating—follow these steps using SQL:

Step 1: Assign Row Numbers to Handle Duplicate Shows #

First, add a row number to each table, partitioned by the Shows column. This ensures duplicate shows are paired in their original order (1st occurrence with 1st, 2nd with 2nd, etc.).

Step 2: Join Tables and Compare Ratings #

Join the two ranked tables on both the Shows name and the row number, then compare the ratings to determine which is higher.

Full Query Example #

Assume your tables are named TableA and TableB, each containing Shows and Rating columns:

WITH RankedTableA AS (
  SELECT 
    Shows,
    Rating,
    -- Assign row number within each Show group to preserve order
    ROW_NUMBER() OVER (PARTITION BY Shows ORDER BY (SELECT NULL)) AS occurrence_num
  FROM TableA
),
RankedTableB AS (
  SELECT 
    Shows,
    Rating,
    ROW_NUMBER() OVER (PARTITION BY Shows ORDER BY (SELECT NULL)) AS occurrence_num
  FROM TableB
)
SELECT 
  rtA.Shows,
  rtA.occurrence_num,
  -- Determine which table has the higher rating
  CASE 
    WHEN rtA.Rating > rtB.Rating THEN 'TableA'
    WHEN rtB.Rating > rtA.Rating THEN 'TableB'
    ELSE 'Ratings are equal'
  END AS higher_rating_source,
  -- Get the highest rating value between the pair
  GREATEST(rtA.Rating, rtB.Rating) AS highest_rating
FROM RankedTableA rtA
INNER JOIN RankedTableB rtB 
  ON rtA.Shows = rtB.Shows 
  AND rtA.occurrence_num = rtB.occurrence_num;

Key Notes: #

• Preserving Original Order: The ORDER BY (SELECT NULL) clause retains the original row order for duplicate shows. If your tables have a specific column defining order (like an ID or timestamp), replace (SELECT NULL) with that column for more reliable ordering.
• Handling Mismatched Occurrences: If one table has more instances of a show than the other, INNER JOIN only returns matching pairs. Use FULL OUTER JOIN to include unmatched rows (you’ll need to handle NULL ratings for those cases).
• Adjust Names: Replace TableA, TableB, Shows, and Rating with your actual table and column names.

内容的提问来源于stack exchange，提问作者tadm123