Have you had to use composite indexes? Tell us about them.

Composite indexes are indexes that are created on multiple columns of a table simultaneously. They are useful when queries filter or sort data based on multiple fields.

For example, if queries frequently use WHERE conditions on columns (last_name, first_name), creating a composite index on these two columns will speed up the search.

It is important to remember that the order of columns in a composite index matters: an index on (A, B) is effective for queries filtering by A or by A and B, but not for B alone.

Example of creating a composite index in SQL:

CREATE INDEX idx_last_first ON users (last_name, first_name);

Using composite indexes helps optimize complex queries and reduce database response time.