When you use query builder, you write a raw SQL code.

The benifit is you can insert user input right in string, and your query remain secure against injections. Additionally, a Nano Queries let you compose queries, and extend it, so you may build complex queries simply.

Let's say you develop a site to search something by its features, for example a movies. Your SQL query may easy takes 100-500 lines. Some part of this query will be a basic, some will be optional depends on provided filters.

With a query builder you may conditionally extend your query like that

if (userInput.rating > 0) {
  filter.and(sql`rating >= ${userInput.rating}`);
}

That's all Query Builder does. It let you avoid to write code like that

const values = [];
const getPlaceholder = (value) => {
  values.push(value);
  return `$${values.length}`;
};

const where = [];
if (year) {
  where.push(`release_year = ${getPlaceholder(year)}`);
}
if (rating) {
  where.push(`rating >= ${getPlaceholder(rating)}`);
}

db.query(
  `SELECT title FROM movies ${where.length ? 'WHERE ' + where.join(' AND ') : ''} LIMIT 100`,
  values,
);