Hello, We were approached to add support for Hive SQL in jOOQ [1], which might be useful for a greater community in general. I've gone through the Hive SQL syntax and I've encountered this interesting clause: The LEFT SEMI JOIN clause [2]
Example: SELECT a.key, a.val FROM a LEFT SEMI JOIN b on (a.key = b.key) My question is: Why "LEFT"? I find this misleading. Compare this with a LEFT OUTER JOIN, which will always return all tuples from relation A at least once, regardless if there are any tuples in relation B matched by the JOIN predicate in "ON". So in other words, a LEFT SEMI JOIN is completely useless as it *should* always return ALL tuples from relation A, compared to a more useful "SEMI JOIN" or "INNER SEMI JOIN". What do you think? Lukas [1]: http://www.jooq.org [2]: https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Joins -- Lukas Eder - Head of R&D | lukas.e...@datageekery.com | +41 44 586 82 56 Data Geekery GmbH | Binzstrasse 23 | CH-8045 Zürich | Switzerland http://www.datageekery.com | Get back in control of your SQLT
