Steve Lau <stevel...@outlook.com> writes:
> I am reading this documentation[1], and it has a sentence that I don’t quite
> understand: "The index columns (key values) can be either simple columns of
> the underlying table or expressions over the table rows.”, I am thinking that
> for the index of expressions, aren’t those expressions over table column?
> e.g., “CREATE INDEX idx_lower_last_name ON users(LOWER(last_name))”,
> “last_name" is a column rather than a row.
Consider
CREATE INDEX idx_lower_name ON users(LOWER(last_name || ' ' || first_name));
regards, tom lane
