Exercise 1: One Query for Blog Totals — Possible Solution
===========================================================

async function publishedStats(where: Prisma.PostWhereInput = {}) {
  const s = await prisma.post.aggregate({
    where:  { published: true, ...where },
    _count: { _all: true },
    _sum:   { viewCount: true },
    _avg:   { viewCount: true },
    _max:   { createdAt: true },
  });

  return {
    posts:      s._count._all,                         // always a number
    totalViews: s._sum.viewCount ?? 0,
    avgViews:   s._avg.viewCount === null ? 0 : Math.round(s._avg.viewCount * 10) / 10,
    latest:     s._max.createdAt?.toISOString() ?? null,
  };
}

console.log(await publishedStats());
// { posts: 18, totalViews: 2140, avgViews: 118.9, latest: "2026-09-20T..." }

console.log(await publishedStats({ title: { contains: "no-such-title" } }));
// { posts: 0, totalViews: 0, avgViews: 0, latest: null }

(Import Prisma from your generated client: import { Prisma } from "./generated/prisma/client")

WHY THIS WORKS AS AN ANSWER
------------------------------
All four figures come from a single aggregate call, so the database
does the work in one round trip. The empty case proves the point from
the chapter: _count returns 0 while _sum, _avg and _max return null,
so each one gets its own fallback. "latest" is left as null on purpose
— there genuinely is no latest post, and a made-up date would mislead.