sqlgen/docs/mathematical_operations.md

Mathematical Operations

The sqlgen library provides a set of mathematical functions for use in queries. These functions are type-safe and map to the appropriate SQL operations for the target database.

Motivating Example

Suppose you want to analyze the ages of children in a family, grouped by their last name, and you want to compute the average, minimum, and maximum age (with some mathematical operations applied):

struct Children {
  std::string last_name;
  double avg_age;
  double max_age_plus_one;
  double min_age_plus_one;
};

const auto get_children =
    select_from<Person>(
        "last_name"_c,
        round(avg(cast<double>("age"_c))).as<"avg_age">(),
        max(cast<double>("age"_c) + 1.0).as<"max_age_plus_one">(),
        (min(cast<double>("age"_c)) + 1.0).as<"min_age_plus_one">()
    )
    | where("age"_c < 18)
    | group_by("last_name"_c)
    | to<std::vector<Children>>;

This query groups people by last name, filters for those under 18, and computes the average age (rounded), the maximum age plus one, and the minimum age plus one.

Mathematical Functions

abs

Returns the absolute value of a numeric expression.

abs("age"_c * (-1)) | as<"abs_age">

ceil / floor

Rounds a numeric value up (ceil) or down (floor) to the nearest integer.

ceil("salary"_c) | as<"salary_ceiled">
floor("salary"_c) | as<"salary_floored">

exp, ln, log2, sqrt

• exp(x): Exponential function (e^x)
• ln(x): Natural logarithm
• log2(x): Base-2 logarithm
• sqrt(x): Square root

round(exp(cast<double>("age"_c)), 2) | as<"exp_age">
round(sqrt(cast<double>("age"_c)), 2) | as<"sqrt_age">

sin, cos, tan

Trigonometric functions.

sin("angle"_c) | as<"sin_angle">
cos("angle"_c) | as<"cos_angle">
tan("angle"_c) | as<"tan_angle">

round

Rounds a numeric value to a specified number of decimal places.

round("price"_c, 2) | as<"rounded_price">