Trait diesel::expression_methods::ExpressionMethods

pub trait ExpressionMethods: Expression + Sized {
    // Provided 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> { ... }
}

Methods present on all expressions, except tuples

Provided Methods

fn eq<T>(self, other: T) -> Eq<Self, T>

where Self::SqlType: SqlType, T: AsExpression<Self::SqlType>,

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.

To get behavior that is more like the Rust = operator you can also use the postgres-specific is_not_distinct_from .

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);

fn ne<T>(self, other: T) -> NotEq<Self, T>

where Self::SqlType: SqlType, T: AsExpression<Self::SqlType>,

Creates a SQL != expression.

Example

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

fn eq_any<T>(self, values: T) -> EqAny<Self, T>

where Self::SqlType: SqlType, T: AsInExpression<Self::SqlType>,

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));

fn ne_all<T>(self, values: T) -> NeAny<Self, T>

where Self::SqlType: SqlType, T: AsInExpression<Self::SqlType>,

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));

fn is_null(self) -> IsNull<Self>

Creates a SQL IS NULL expression.

Example

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

fn is_not_null(self) -> IsNotNull<Self>

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);

fn gt<T>(self, other: T) -> Gt<Self, T>

where Self::SqlType: SqlType, T: AsExpression<Self::SqlType>,

Creates a SQL > expression.

Example

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

fn ge<T>(self, other: T) -> GtEq<Self, T>

where Self::SqlType: SqlType, T: AsExpression<Self::SqlType>,

Creates a SQL >= expression.

Example

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

fn lt<T>(self, other: T) -> Lt<Self, T>

where Self::SqlType: SqlType, T: AsExpression<Self::SqlType>,

Creates a SQL < expression.

Example

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

fn le<T>(self, other: T) -> LtEq<Self, T>

where Self::SqlType: SqlType, T: AsExpression<Self::SqlType>,

Creates a SQL <= expression.

Example

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

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>,

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);

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>,

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);

fn desc(self) -> Desc<Self>

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);

fn asc(self) -> Asc<Self>

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())
    };

Object Safety

This trait is not object safe.

Implementors

impl<T> ExpressionMethods for T

where T: Expression, T::SqlType: SingleValue,