Trait diesel::prelude::ExpressionMethods

source · [−]
pub trait ExpressionMethods: Expression + Sized {

Show 14 methods    fn eq<T>(self, other: T) -> Eq<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
    { ... }
    fn ne<T>(self, other: T) -> NotEq<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
    { ... }
    fn eq_any<T>(self, values: T) -> EqAny<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsInExpression<Self::SqlType>,
    { ... }
    fn ne_all<T>(self, values: T) -> NeAny<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsInExpression<Self::SqlType>,
    { ... }
    fn is_null(self) -> IsNull<Self> { ... }
    fn is_not_null(self) -> IsNotNull<Self> { ... }
    fn gt<T>(self, other: T) -> Gt<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
    { ... }
    fn ge<T>(self, other: T) -> GtEq<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
    { ... }
    fn lt<T>(self, other: T) -> Lt<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
    { ... }
    fn le<T>(self, other: T) -> LtEq<Self, T>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
    { ... }
    fn between<T, U>(self, lower: T, upper: U) -> Between<Self, T, U>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
        U: AsExpression<Self::SqlType>,
    { ... }
    fn not_between<T, U>(self, lower: T, upper: U) -> NotBetween<Self, T, U>
    where
        Self::SqlType: SqlType,
        T: AsExpression<Self::SqlType>,
        U: AsExpression<Self::SqlType>,
    { ... }
    fn desc(self) -> Desc<Self> { ... }
    fn asc(self) -> Asc<Self> { ... }

}
Expand description

Methods present on all expressions, except tuples

Provided Methods

Creates a SQL = expression.

Note that this function follows SQL semantics around None/null values, so eq(None) will never match. Use is_null instead.

Example
let data = users.select(id).filter(name.eq("Sean"));
assert_eq!(Ok(1), data.first(connection));

Matching against None follows SQL semantics:

let data = animals
    .select(species)
    .filter(name.eq::<Option<String>>(None))
    .first::<String>(connection);
assert_eq!(Err(diesel::NotFound), data);

let data = animals
    .select(species)
    .filter(name.is_null())
    .first::<String>(connection)?;
assert_eq!("spider", data);

Creates a SQL != expression.

Example
let data = users.select(id).filter(name.ne("Sean"));
assert_eq!(Ok(2), data.first(connection));

Creates a SQL IN statement.

Queries using this method will not typically be placed in the prepared statement cache. However, in cases when a subquery is passed to the method, that query will use the cache (assuming the subquery itself is safe to cache). On PostgreSQL, this method automatically performs a = ANY() query.

Example
let data = users::table.select(users::id).filter(users::name.eq_any(vec!["Sean", "Jim"]));
assert_eq!(Ok(vec![1, 3]), data.load(connection));

// Calling `eq_any` with an empty array is the same as doing `WHERE 1=0`
let data = users::table.select(users::id).filter(users::name.eq_any(Vec::<String>::new()));
assert_eq!(Ok(vec![]), data.load::<i32>(connection));

// Calling `eq_any` with a subquery is the same as using
// `WHERE {column} IN {subquery}`.

let subquery = users::table.filter(users::name.eq("Sean")).select(users::id).into_boxed();
let data = posts::table.select(posts::id).filter(posts::user_id.eq_any(subquery));
assert_eq!(Ok(vec![1, 2]), data.load::<i32>(connection));

Creates a SQL NOT IN statement.

Queries using this method will not be placed in the prepared statement cache. On PostgreSQL, this method automatically performs a != ALL() query.

Example
let data = users.select(id).filter(name.ne_all(vec!["Sean", "Jim"]));
assert_eq!(Ok(vec![2]), data.load(connection));

let data = users.select(id).filter(name.ne_all(vec!["Tess"]));
assert_eq!(Ok(vec![1, 3]), data.load(connection));

// Calling `ne_any` with an empty array is the same as doing `WHERE 1=1`
let data = users.select(id).filter(name.ne_all(Vec::<String>::new()));
assert_eq!(Ok(vec![1, 2, 3]), data.load(connection));

Creates a SQL IS NULL expression.

Example
let data = animals
    .select(species)
    .filter(name.is_null())
    .first::<String>(connection)?;
assert_eq!("spider", data);

Creates a SQL IS NOT NULL expression.

Example
let data = animals
    .select(species)
    .filter(name.is_not_null())
    .first::<String>(connection)?;
assert_eq!("dog", data);

Creates a SQL > expression.

Example
let data = users
    .select(name)
    .filter(id.gt(1))
    .first::<String>(connection)?;
assert_eq!("Tess", data);

Creates a SQL >= expression.

Example
let data = users
    .select(name)
    .filter(id.ge(2))
    .first::<String>(connection)?;
assert_eq!("Tess", data);

Creates a SQL < expression.

Example
let data = users
    .select(name)
    .filter(id.lt(2))
    .first::<String>(connection)?;
assert_eq!("Sean", data);

Creates a SQL <= expression.

Example
let data = users
    .select(name)
    .filter(id.le(2))
    .first::<String>(connection)?;
assert_eq!("Sean", data);

Creates a SQL BETWEEN expression using the given lower and upper bounds.

Example
let data = animals
    .select(species)
    .filter(legs.between(2, 6))
    .first(connection);
assert_eq!(Ok("dog".to_string()), data);

Creates a SQL NOT BETWEEN expression using the given lower and upper bounds.

Example
let data = animals
    .select(species)
    .filter(legs.not_between(2, 6))
    .first::<String>(connection)?;
assert_eq!("spider", data);

Creates a SQL DESC expression, representing this expression in descending order.

Example
let names = users
    .select(name)
    .order(name.desc())
    .load::<String>(connection)?;
assert_eq!(vec!["Tess", "Sean"], names);

Creates a SQL ASC expression, representing this expression in ascending order.

This is the same as leaving the direction unspecified. It is useful if you need to provide an unknown ordering, and need to box the return value of a function.

Example
let ordering: Box<dyn BoxableExpression<users, DB, SqlType = NotSelectable>> =
    if order == "name" {
        Box::new(name.desc())
    } else {
        Box::new(id.asc())
    };

Implementors