Postgres Join Strategies - Nested Loop Join, Hash Join, Merge Join

In this video, I share with you how Postgres Join strategies work. I will explain in details step by step how these 3 join algorithms operate: Nested Loop Join, Hash Join and Merge Join.
#postgres #queryplan #liftandshiftdev #postgresql #backend #database #sql #joinstrategies #mergejoin #hashjoin #nestedloopjoin
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[@lotsa2000]

Isn't the merge join at the end incorrect since the second set wasn't sorted first? From what I'm seeing, merge join requires both sets to be sorted first.

[@hardikrajpal2410]

Yep, definitely needs to be sorted first.

[@thinethnadarajah7299]

Merge join explaination is wrong. Second ist has to be sorted

[@VictorLima-xv3rq]

Very easy to understand, thank u a lot

[@atulmarkan3394]

In the merge join, you did not pick/match employe id 4. Why you are not considering that record. as per condition it should be part of the result. Can you please update on this?

[@RavilKhalilov]

For that, you have to create pre-sorted index in the salary table. In this case, Merge Join will go through all values in salary table, but in the sorted way.