DT
Drizzle Team•2y ago
AstroBear

Why does `sum` return `SQL<string | null>`?

I was trying to use the sum aggregate function and I noticed that it returns a string. Why is that? 
/**
 * Returns the sum of all non-null values in `expression`.
 *
 * ## Examples
 *
 * \`\`\`ts
 * // Sum of every employee's salary
 * db.select({ value: sum(employees.salary) }).from(employees)
 * \`\`\`
 *
 * @see sumDistinct to get the sum of all non-null and non-duplicate values in `expression`
 */
export declare function sum(expression: SQLWrapper): SQL<string | null>;
/**
 * Returns the sum of all non-null values in `expression`.
 *
 * ## Examples
 *
 * \`\`\`ts
 * // Sum of every employee's salary
 * db.select({ value: sum(employees.salary) }).from(employees)
 * \`\`\`
 *
 * @see sumDistinct to get the sum of all non-null and non-duplicate values in `expression`
 */
export declare function sum(expression: SQLWrapper): SQL<string | null>;
6 Replies
Mykhailo
Mykhailo•2y ago
@AstroBear If you are using drizzle function sum(), it is designed this way. If you are using sql, drizzle cannot accurately determine the type without user input. So the best way is to determine type by yourself 
sql`sum(${expression})`.mapWith(Number);
sql`sum(${expression})`.mapWith(Number);
AstroBear
AstroBearOP•2y ago
Thanks, I was using the drizzle sum agg helper. I ended up just using Number() at the end, but I was wondering why it was decided it had to return a string
Mykhailo
Mykhailo•2y ago
This is drizzle sum agg helper, so it is just designed this way 
function sum(expression) {
  return sql`sum(${expression})`.mapWith(String);
}
function sum(expression) {
  return sql`sum(${expression})`.mapWith(String);
}
AstroBear
AstroBearOP•2y ago
Got it, ty. I guess it is mapped to String for some sort of compatibility.
Trey
Trey•2y ago
"Just designed this way", is not a great answer. I will also use this workaround but it would be great if someone who knows the history of sum can answer why it returns string | null.
Angelelz
Angelelz•2y ago
Because the sum function can theoretically return null If no columns are returned by your query, sum will return null A string was used because drizzle cannot warrantee that the number returned by the database will be representable in a JS number It could be a bigint

Did you find this page helpful?