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LoginFind items in a table that match a set of conditions in another table
General Tech Technology & Software 2 years ago
Posted on 16 Aug 2022, this text provides information on Technology & Software related to General Tech. Please note that while accuracy is prioritized, the data presented might not be entirely correct or up-to-date. This information is offered for general knowledge and informational purposes only, and should not be considered as a substitute for professional advice.
manpreet 2 years ago
This is the standard logic to find subsets, but 15 minutes for two not really big tables is really a lot.
The join might return a huge result intermediate set (it's a m-n-join), you can check it using:
SELECT COUNT(*)
FROM #TABLE1 AS T1
JOIN #TABLE2 AS T2 ON T2.EXPORT = T1.EXPORTYour query can be simplified a bit using a Group Count before the join:
WITH cte AS
(
SELECT *,
COUNT(*) OVER (PARTITION BY SETID) AS cnt
FROM #TABLE1
)
SELECT SETID, COUNTRY
FROM cte
JOIN #TABLE2 AS T2
ON T2.EXPORT = cte.EXPORT
GROUP BY SETID, COUNTRY
HAVING COUNT(*) = MAX(cte.cnt)
ORDER BY SETIDBut I don't expect this to improve runtime (unless the optimizer did a very stupid plan before)
Edit:
As expected, most of the runtime is caused by the huge number (1,500,000,000) of rows in the intermediate result set. For a similar problem (exactly matching two sets) I used a solution based on joining comma-delimited strings of all values in a group (which was very efficient on a Teradata system). This logic can be modified for subsets, but I don't really know about efficiency.
This is the algorithm:
For each country create a comma-delimited list like this:
,FOOD,,GARMENT,,STEEL,,TECHNOLOGY,For each set create a comma-delimited list like this:
%,GARMENT,%,TECHNOLOGY,%And then simply join using a LIKE (the additional commas are needed to prevent matching partial values, e.g. 'TECHNO' matching 'TECHNOLOGY'):
WITH cte1 AS
(
SELECT SETID,
STUFF((SELECT ',%,' + EXPORT
FROM #TABLE1 AS t2
WHERE t.SETID = t2.SETID
ORDER BY EXPORT
FOR XML PATH('')) + ',%', 1, 1, '') AS x
FROM #TABLE1 AS t
GROUP BY setid
)
,cte2 AS
(
SELECT COUNTRY,
(SELECT ',' + EXPORT + ','
FROM #TABLE2 AS t2
WHERE t.COUNTRY = t2.COUNTRY
ORDER BY EXPORT
FOR XML PATH('')) AS x
FROM #TABLE2 AS t
GROUP BY COUNTRY
)
SELECT cte1.SETID, cte2.COUNTRY
FROM
manpreet![Tuteehub forum best answer]()
Best Answer
2 years ago
I have two tables. Table 1 has sets of EXPORT conditions: e.g., SET 1 has FOOD, GARMENT, and TECHNOLOGY, and SET 2 contains GARMENT and TECHNOLOGY.
Table 2 has a list of countries with different types of exports.
I would like to find countries that satisfy each set of the conditions. A country satisfies a set of conditions if it meets all the conditions in a set (even if it may meet additional conditions) -- For example, CHINA satisfies SET 1 even though it also meets the additional condition STEEL.
The expected output is something like:
Here's the query I have. It does the job, but I wonder if there is a way to make it perform better.Currently, when Table 1 has 5000 rows (approx. 600 sets of conditions), and Table 2 has 6 million rows, it takes 15 minutes to get the output.
Code for generating sample tables: