Why 'A left join B' and 'B right join A' are different in Clickhouse?

Asked Mar 05 '21 at 07:59

Active Mar 07 '21 at 10:19

Viewed 48 times

I don't care the order of the query result. From relational algebra point of view, these should be the same. The two queries give different results in Clickhouse.

Querys:

select count(*) from A left join B on A.product_id = B.product_id and A.date = B.date

got 20000 rows;

select count(*) from B right join A on A.product_id = B.product_id and A.date = B.date

gives 300000 rows instead.

edited Mar 07 '21 at 10:19

Michael Entin

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asked Mar 05 '21 at 07:59

hay hashi

Adding sample data to your question would not only help us, it might also explain your current observations. – Tim Biegeleisen Mar 05 '21 at 08:03
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Logically they should produce the same result, so something else is happening here. Please try to reduce some sample data to a [mcve]. – Damien_The_Unbeliever Mar 05 '21 at 08:05
It will produce different results if one table is distributed and another is not. – Denny Crane Mar 05 '21 at 13:14

Why 'A left join B' and 'B right join A' are different in Clickhouse?

0 Answers0