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What is meant by "secondary index" in this lesson?

Hi! There is a sentence “All indexes are secondary indexes when using MyISAM as the database engine” in a place with discussion about non-clustered indexes, which makes it a bit hard to understand, what is meant my that “secondary index” exactly?

Do you mean that there is one clustered index which is in fact the table, and all other indexes are non-clustered = secondary?


Course: https://www.educative.io/collection/5352985413550080/6335716377231360
Lesson: https://www.educative.io/collection/page/5352985413550080/6335716377231360/5601324986007552

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Hi @Dmitry_Polovinkin, Thank you for contacting the Educative team with your query!
The sentence “All indexes are secondary indexes when using MyISAM as the database engine” means that there is no clustered index because by default the “MyISAM Storage Engine” does not support clustered indexes leaving behind all indexes as secondary indexes.

Hope you understand and have an amazing learning experience on Educative!

Thanks for a clarification! But it’s still quite hard to get - what does the term “secondary index” means at all, among a lot of different types on indexes I’ve never met a definition of “secondary”. If there are secondary indexes - there should be “primary” then? thx!


Course: https://www.educative.io/collection/5352985413550080/6335716377231360
Lesson: https://www.educative.io/collection/page/5352985413550080/6335716377231360/6016287047155712

@Rehan_Butt hi, so can you clarify it please?