Struct diesel::query_builder::DeleteStatement

#[must_use = "Queries are only executed when calling `load`, `get_result` or similar."]
pub struct DeleteStatement<T, U, Ret = NoReturningClause> { /* fields omitted */ }

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.

Methods

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

type QueryId = DeleteStatement<<T as QueryId>::QueryId, <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> Query for DeleteStatement<T, U, ReturningClause<Ret>> where     T: Table,     Ret: SelectableExpression<T>,

type SqlType = Ret::SqlType

The SQL type that this query represents.

impl<T, U, Ret, DB> QueryFragment<DB> for DeleteStatement<T, U, Ret> where     DB: Backend,     T: Table,     T::FromClause: QueryFragment<DB>,     U: QueryFragment<DB>,     Ret: QueryFragment<DB>,

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

Walk over this QueryFragment for all passes.

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

Converts this QueryFragment to its SQL representation.

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

Serializes all bind parameters in this query.

fn is_safe_to_cache_prepared(&self) -> QueryResult<bool>

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

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 = <Self::Query as Query>::SqlType

The SQL type of Self::Query

type Query = DeleteStatement<T, U, ReturningClause<T::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>>,

type Output = BoxedDeleteStatement<'a, DB, T, Ret>

The return type of internal_into_boxed

fn internal_into_boxed(self) -> Self::Output

See the trait documentation.

impl<T, U, Ret, Predicate> FilterDsl<Predicate> for DeleteStatement<T, U, Ret> where     U: WhereAnd<Predicate>,     Predicate: AppearsOnTable<T>,

type Output = DeleteStatement<T, U::Output, Ret>

The type returned by .filter.

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

See the trait documentation.

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

fn execute(self, conn: &Conn) -> QueryResult<usize> where     Conn: Connection,     Self: ExecuteDsl<Conn>,

Executes the given command, returning the number of rows affected.

fn load<U>(self, conn: &Conn) -> QueryResult<Vec<U>> where     Self: LoadQuery<Conn, U>,

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

fn get_result<U>(self, conn: &Conn) -> QueryResult<U> where     Self: LoadQuery<Conn, U>,

Runs the command, and returns the affected row.

fn get_results<U>(self, conn: &Conn) -> QueryResult<Vec<U>> where     Self: LoadQuery<Conn, U>,

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

fn first<U>(self, conn: &Conn) -> QueryResult<U> where     Self: LimitDsl,     Limit<Self>: LoadQuery<Conn, U>,

Attempts to load a single record.

impl<T: Copy, U: Copy, Ret: Copy> Copy for DeleteStatement<T, U, Ret>

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

fn clone(&self) -> DeleteStatement<T, U, Ret>

Returns a copy of the value.

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

Performs copy-assignment from source.

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

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

Formats the value using the given formatter.