dilipbiswal commented on issue #23982: [SQL][MINOR] Reconcile the join types between data frame and sql interface URL: https://github.com/apache/spark/pull/23982#issuecomment-469927252 @maropu Thank you. Very few systems i could find that expose the semi and anti join types to users. I checked oracle, mysql, postgress, db2, Following are the systems i could find that expose this. 1) Makes LEFT optional for both semi and anti join from the below link. https://docs.microsoft.com/en-us/u-sql/statements-and-expressions/select/from/joins/semijoin 2) Hive exposes only LEFT SEMI JOIN. However, LEFT SEMI and SEMI return different output. Not sure if its a bug. This is one of the reason, i was though removing the ambiguity would be better. ``` Connected to: Apache Hive (version 3.1.0.3.1.0.0-78) Driver: Hive JDBC (version 3.1.0.3.1.0.0-78) Transaction isolation: TRANSACTION_REPEATABLE_READ Beeline version 3.1.0.3.1.0.0-78 by Apache Hive ``` select * from a1 left semi join a2; ``` +--------+--------+ | a1.c1 | a1.c2 | +--------+--------+ | 1 | 1 | +--------+--------+ ``` select * from a1 semi join a2; => left is not specified ``` +----------+----------+--------+--------+ | semi.c1 | semi.c2 | a2.c3 | a2.c4 | +----------+----------+--------+--------+ | 1 | 1 | 2 | 2 | | 1 | 1 | 3 | 3 | +----------+----------+--------+--------+ ```
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