Struct diesel::query_builder::DeleteStatement

pub struct DeleteStatement<T: QuerySource, U, Ret = NoReturningClause> { /* private fields */ }

Represents a SQL DELETE statement.

The type parameters on this struct represent:

• T: The table we are deleting from.
• U: The WHERE clause of this query. The exact types used to represent this are private, and you should not make any assumptions about them.
• Ret: The RETURNING clause of this query. The exact types used to represent this are private. You can safely rely on the default type representing the lack of a RETURNING clause.

Implementations

impl<T: QuerySource, U> DeleteStatement<T, U, NoReturningClause>

pub fn filter<Predicate>(self, predicate: Predicate) -> Filter<Self, Predicate>

where Self: FilterDsl<Predicate>,

Adds the given predicate to the WHERE clause of the statement being constructed.

If there is already a WHERE clause, the predicate will be appended with AND. There is no difference in behavior between delete(table.filter(x)) and delete(table).filter(x).

Example

let deleted_rows = diesel::delete(users)
    .filter(name.eq("Sean"))
    .execute(connection);
assert_eq!(Ok(1), deleted_rows);

let expected_names = vec!["Tess".to_string()];
let names = users.select(name).load(connection);

assert_eq!(Ok(expected_names), names);

pub fn or_filter<Predicate>( self, predicate: Predicate ) -> OrFilter<Self, Predicate>

where Self: OrFilterDsl<Predicate>,

Adds to the WHERE clause of a query using OR

If there is already a WHERE clause, the result will be (old OR new). Calling foo.filter(bar).or_filter(baz) is identical to foo.filter(bar.or(baz)). However, the second form is much harder to do dynamically.

Example

let deleted_rows = diesel::delete(users)
    .filter(name.eq("Sean"))
    .or_filter(name.eq("Tess"))
    .execute(connection);
assert_eq!(Ok(2), deleted_rows);

let num_users = users.count().first(connection);

assert_eq!(Ok(0), num_users);

pub fn into_boxed<'a, DB>(self) -> IntoBoxed<'a, Self, DB>

where DB: Backend, Self: BoxedDsl<'a, DB>,

Boxes the WHERE clause of this delete statement.

This is useful for cases where you want to conditionally modify a query, but need the type to remain the same. The backend must be specified as part of this. It is not possible to box a query and have it be useable on multiple backends.

A boxed query will incur a minor performance penalty, as the query builder can no longer be inlined by the compiler. For most applications this cost will be minimal.

Example

let mut query = diesel::delete(users)
    .into_boxed();

if params["sean_has_been_a_jerk"] {
    query = query.filter(name.eq("Sean"));
}

let deleted_rows = query.execute(connection)?;
assert_eq!(1, deleted_rows);

let expected_names = vec!["Tess"];
let names = users.select(name).load::<String>(connection)?;

assert_eq!(expected_names, names);

impl<T: QuerySource, U> DeleteStatement<T, U, NoReturningClause>

pub fn returning<E>( self, returns: E ) -> DeleteStatement<T, U, ReturningClause<E>>

where E: SelectableExpression<T>, DeleteStatement<T, U, ReturningClause<E>>: Query,

Specify what expression is returned after execution of the delete.

Examples

Deleting a record:

let deleted_name = diesel::delete(users.filter(name.eq("Sean")))
    .returning(name)
    .get_result(connection);
assert_eq!(Ok("Sean".to_string()), deleted_name);

Trait Implementations

impl<T, U> AsQuery for DeleteStatement<T, U, NoReturningClause>

where T: Table, T::AllColumns: SelectableExpression<T>, DeleteStatement<T, U, ReturningClause<T::AllColumns>>: Query,

type SqlType = <<DeleteStatement<T, U> as AsQuery>::Query as Query>::SqlType

The SQL type of Self::Query

type Query = DeleteStatement<T, U, ReturningClause<<T as Table>::AllColumns>>

What kind of query does this type represent?

fn as_query(self) -> Self::Query

Converts a type which semantically represents a SQL query into the actual query being executed. See the trait level docs for more.

impl<'a, T, U, Ret, DB> BoxedDsl<'a, DB> for DeleteStatement<T, U, Ret>

where U: Into<BoxedWhereClause<'a, DB>>, T: QuerySource,

type Output = DeleteStatement<T, BoxedWhereClause<'a, DB>, Ret>

The return type of internal_into_boxed

fn internal_into_boxed(self) -> Self::Output

See the trait documentation.

impl<T, U, Ret> Clone for DeleteStatement<T, U, Ret>

where T: QuerySource, FromClause<T>: Clone, U: Clone, Ret: Clone,

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T, U, Ret> Debug for DeleteStatement<T, U, Ret>

where T: QuerySource, FromClause<T>: Debug, U: Debug, Ret: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T, U, Ret, Predicate> FilterDsl<Predicate> for DeleteStatement<T, U, Ret>

where U: WhereAnd<Predicate>, Predicate: AppearsOnTable<T>, T: QuerySource,

type Output = DeleteStatement<T, <U as WhereAnd<Predicate>>::Output, Ret>

The type returned by .filter.

fn filter(self, predicate: Predicate) -> Self::Output

See the trait documentation.

impl<T, U, Ret, Predicate> OrFilterDsl<Predicate> for DeleteStatement<T, U, Ret>

where T: QuerySource, U: WhereOr<Predicate>, Predicate: AppearsOnTable<T>,

type Output = DeleteStatement<T, <U as WhereOr<Predicate>>::Output, Ret>

The type returned by .filter.

fn or_filter(self, predicate: Predicate) -> Self::Output

See the trait documentation.

impl<T, U, Ret> Query for DeleteStatement<T, U, ReturningClause<Ret>>

where T: Table, Ret: SelectableExpression<T>,

type SqlType = <Ret as Expression>::SqlType

The SQL type that this query represents.

impl<T, U, Ret, DB> QueryFragment<DB> for DeleteStatement<T, U, Ret>

where DB: Backend + DieselReserveSpecialization, T: Table, FromClause<T>: QueryFragment<DB>, U: QueryFragment<DB>, Ret: QueryFragment<DB>,

fn walk_ast<'b>(&'b self, out: AstPass<'_, 'b, DB>) -> QueryResult<()>

Walk over this QueryFragment for all passes.

fn to_sql(&self, out: &mut DB::QueryBuilder, backend: &DB) -> QueryResult<()>

Available on crate feature i-implement-a-third-party-backend-and-opt-into-breaking-changes only.

Converts this QueryFragment to its SQL representation.

fn collect_binds<'b>( &'b self, out: &mut DB::BindCollector<'b>, metadata_lookup: &mut DB::MetadataLookup, backend: &'b DB ) -> QueryResult<()>

Available on crate feature i-implement-a-third-party-backend-and-opt-into-breaking-changes only.

Serializes all bind parameters in this query.

fn is_safe_to_cache_prepared(&self, backend: &DB) -> QueryResult<bool>

Available on crate feature i-implement-a-third-party-backend-and-opt-into-breaking-changes only.

Is this query safe to store in the prepared statement cache?

fn is_noop(&self, backend: &DB) -> QueryResult<bool>

Available on crate feature i-implement-a-third-party-backend-and-opt-into-breaking-changes only.

Does walking this AST have any effect?

impl<T, U, Ret> QueryId for DeleteStatement<T, U, Ret>

where T: QuerySource + QueryId + 'static, U: QueryId, Ret: QueryId,

type QueryId = DeleteStatement<T, <U as QueryId>::QueryId, <Ret as QueryId>::QueryId>

A type which uniquely represents Self in a SQL query.

const HAS_STATIC_QUERY_ID: bool = _

Can the SQL generated by Self be uniquely identified by its type?

fn query_id() -> Option<TypeId>

Returns the type id of Self::QueryId if Self::HAS_STATIC_QUERY_ID. Returns None otherwise.

impl<T, U, Ret, Conn> RunQueryDsl<Conn> for DeleteStatement<T, U, Ret>

where T: QuerySource,

fn load<'query, U>(self, conn: &mut Conn) -> QueryResult<Vec<U>>

where Self: LoadQuery<'query, Conn, U>,

Executes the given query, returning a Vec with the returned rows.

fn load_iter<'conn, 'query: 'conn, U, B>( self, conn: &'conn mut Conn ) -> QueryResult<Self::RowIter<'conn>>

where U: 'conn, Self: LoadQuery<'query, Conn, U, B> + 'conn,

Executes the given query, returning an Iterator with the returned rows.

fn get_result<'query, U>(self, conn: &mut Conn) -> QueryResult<U>

where Self: LoadQuery<'query, Conn, U>,

Runs the command, and returns the affected row.

fn get_results<'query, U>(self, conn: &mut Conn) -> QueryResult<Vec<U>>

where Self: LoadQuery<'query, Conn, U>,

Runs the command, returning an Vec with the affected rows.