diesel/expression/functions/
aggregate_folding.rs

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1use crate::expression::functions::define_sql_function;
2use crate::sql_types::Foldable;
3
4define_sql_function! {
5    /// Represents a SQL `SUM` function. This function can only take types which are
6    /// Foldable.
7    ///
8    /// # Examples
9    ///
10    /// ```rust
11    /// # include!("../../doctest_setup.rs");
12    /// # use diesel::dsl::*;
13    /// #
14    /// # fn main() {
15    /// #     use schema::animals::dsl::*;
16    /// #     let connection = &mut establish_connection();
17    /// assert_eq!(Ok(Some(12i64)), animals.select(sum(legs)).first(connection));
18    /// # }
19    /// ```
20    #[aggregate]
21    fn sum<ST: Foldable>(expr: ST) -> ST::Sum;
22}
23
24define_sql_function! {
25    /// Represents a SQL `AVG` function. This function can only take types which are
26    /// Foldable.
27    ///
28    /// # Examples
29    ///
30    /// ```rust
31    /// # include!("../../doctest_setup.rs");
32    /// # use diesel::dsl::*;
33    /// # #[cfg(feature = "numeric")]
34    /// # extern crate bigdecimal;
35    /// #
36    /// # fn main() {
37    /// #     run_test().unwrap();
38    /// # }
39    /// #
40    /// # table! {
41    /// #     numbers (number) {
42    /// #         number -> Integer,
43    /// #     }
44    /// # }
45    /// #
46    /// # #[cfg(all(feature = "numeric", any(feature = "postgres", not(feature = "sqlite"))))]
47    /// # fn run_test() -> QueryResult<()> {
48    /// #     use bigdecimal::BigDecimal;
49    /// #     use self::numbers::dsl::*;
50    /// #     let conn = &mut establish_connection();
51    /// #     diesel::sql_query("DROP TABLE IF EXISTS numbers").execute(conn)?;
52    /// #     diesel::sql_query("CREATE TABLE numbers (number INTEGER)").execute(conn)?;
53    /// diesel::insert_into(numbers)
54    ///     .values(&vec![number.eq(1), number.eq(2)])
55    ///     .execute(conn)?;
56    /// let average = numbers.select(avg(number)).get_result(conn)?;
57    /// let expected = "1.5".parse::<BigDecimal>().unwrap();
58    /// assert_eq!(Some(expected), average);
59    /// #     Ok(())
60    /// # }
61    /// #
62    /// # #[cfg(not(all(feature = "numeric", any(feature = "postgres", not(feature = "sqlite")))))]
63    /// # fn run_test() -> QueryResult<()> {
64    /// #     Ok(())
65    /// # }
66    #[aggregate]
67    fn avg<ST: Foldable>(expr: ST) -> ST::Avg;
68}
diesel/expression/functions/aggregate_folding.rs

diesel/expression/functions/
aggregate_folding.rs
