Sign Up to our social questions and Answers Engine to ask questions, answer people’s questions, and connect with other people.
Login to our social questions & Answers Engine to ask questions answer people’s questions & connect with other people.
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Please briefly explain why you feel this question should be reported.
Please briefly explain why you feel this answer should be reported.
Please briefly explain why you feel this user should be reported.
I am confused with these 3 terms: cover index, compound index and multi-fields index.
Are they same things? or each of them has subtle difference?
Thanks
Compound index and multi-fields Index are the same. Other terms for the same are Multi-Column Index and Concatenated Index.
That are indexes that contain more than one column.
I suspect that Cover Index is actually Covering Index which is something entirely different, better described as Index-Only-Scan.
That is not a property of an index, it is describing how the index is used. It means that a particular query can be satisfied with data from the index only, not needing to read the table data. (Note: An index copies data from the table).
A single index can be a covering-index for one query, but not cover another query (that accesses columns not included (covered) in the index). Think of “The index covers the entire query.”
More about database indexing: http://use-the-index-luke.com/