SQL Indexing not improving speed-CodePudding

Given an SQL database with index for (startpage, endpage), with a relation Articles(*ID*, title, startpage, endpage), why isn't a query

SELECT title 
FROM Articles 
WHERE endpage = 100;

sped up by the previous index?

Apologies for this peculiar question as it came from a practice paper without explanation.

CodePudding user response：

Why the index shown does not help that query: because endpage is not the leftmost column of the index.

See my answer to Does Order of Fields of Multi-Column Index in MySQL Matter for more explanation (that question is about MySQL, but the answer should apply to any implementation of B-tree indexes).

CodePudding user response：

SELECT * FROM myTable WHERE status='active' and dateAdded='2010-10-01'
  try this query.