Hive SQL: How To Write A LEFT SEMI JOIN

  • For this video, we use a self join table since our join will only involve one table. Since we join the table onto itself, any column that we use in the join condition will match provided that we don’t change any part of the condition (which we do in our example and I show why).
  • As a quick reminder, not all SQL languages may support the exact syntax shown. Different SQL languages may have different approaches to solving the same problem or developing the same solution.
  • As we see with the results of the INNER JOIN, what output issue occurs when we join Table1 and Table2 when it comes to columns? For developers with application experience, what would be the issue here? Keep in mind that with INNER JOINs, this is seldom an issue, but worth considering in this case because it does come up.
  • How does a LEFT SEMI JOIN solve the above issue?
  • When would we consider using a LEFT SEMI JOIN? What could be the possible issue?

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Data | Development | Security.

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