single_value_dsl.rs - source

Files

aho_corasick

autiter.rs full.rs lib.rs

bigdecimal

lib.rs macros.rs

bitflags

byteorder

cfg_if

chrono

format

mod.rs parse.rs parsed.rs scan.rs strftime.rs

naive

date.rs datetime.rs internals.rs isoweek.rs time.rs

offset

fixed.rs local.rs mod.rs utc.rs

sys

date.rs datetime.rs div.rs lib.rs round.rs sys.rs

diesel

associations

belongs_to.rs mod.rs

connection

mod.rs statement_cache.rs transaction_manager.rs

expression

expression_methods

bool_expression_methods.rs eq_all.rs escape_expression_methods.rs global_expression_methods.rs mod.rs text_expression_methods.rs

macros

internal.rs mod.rs ops.rs query_id.rs static_cond.rs tuples.rs

migration

errors.rs mod.rs

mysql

connection

stmt

iterator.rs metadata.rs mod.rs

bind.rs mod.rs raw.rs url.rs

query_builder

mod.rs query_fragment_impls.rs

types

date_and_time.rs mod.rs numeric.rs

backend.rs bind_collector.rs mod.rs

pg

connection

stmt

cursor.rs mod.rs raw.rs result.rs row.rs

expression

extensions

interval_dsl.rs mod.rs

array.rs array_comparison.rs date_and_time.rs expression_methods.rs helper_types.rs mod.rs operators.rs

query_builder

distinct_on.rs mod.rs query_fragment_impls.rs

serialize

mod.rs write_tuple.rs

types

date_and_time

chrono.rs deprecated_time.rs mod.rs quickcheck_impls.rs std_time.rs

floats

mod.rs quickcheck_impls.rs

array.rs integers.rs json.rs mod.rs money.rs network_address.rs numeric.rs primitives.rs ranges.rs record.rs uuid.rs uuid_v0_7.rs

upsert

mod.rs on_conflict_actions.rs on_conflict_clause.rs on_conflict_extension.rs on_conflict_target.rs

backend.rs metadata_lookup.rs mod.rs transaction.rs

query_builder

delete_statement

insert_statement

column_list.rs insert_from_select.rs mod.rs

nodes

select_statement

boxed.rs dsl_impls.rs mod.rs

update_statement

changeset.rs mod.rs target.rs

ast_pass.rs bind_collector.rs clause_macro.rs debug_query.rs distinct_clause.rs functions.rs group_by_clause.rs limit_clause.rs locking_clause.rs mod.rs offset_clause.rs order_clause.rs query_id.rs returning_clause.rs select_clause.rs sql_query.rs where_clause.rs

query_dsl

belonging_to_dsl.rs boxed_dsl.rs distinct_dsl.rs filter_dsl.rs group_by_dsl.rs join_dsl.rs limit_dsl.rs load_dsl.rs locking_dsl.rs mod.rs nullable_select_dsl.rs offset_dsl.rs order_dsl.rs save_changes_dsl.rs select_dsl.rs single_value_dsl.rs

query_source

joins.rs mod.rs peano_numbers.rs

sql_types

fold.rs mod.rs ops.rs ord.rs

sqlite

connection

functions.rs mod.rs raw.rs serialized_value.rs sqlite_value.rs statement_iterator.rs stmt.rs

query_builder

types

date_and_time

chrono.rs mod.rs

mod.rs numeric.rs

backend.rs mod.rs

type_impls

date_and_time.rs decimal.rs floats.rs integers.rs mod.rs option.rs primitives.rs tuples.rs

types

backend.rs data_types.rs deserialize.rs insertable.rs lib.rs r2d2.rs result.rs row.rs serialize.rs util.rs

diesel_derives

as_changeset.rs as_expression.rs associations.rs diagnostic_shim.rs diesel_numeric_ops.rs field.rs from_sql_row.rs identifiable.rs insertable.rs lib.rs meta.rs model.rs query_id.rs queryable.rs queryable_by_name.rs resolved_at_shim.rs sql_type.rs util.rs

diesel_migrations

env_logger

lib.rs regex.rs

idna

lib.rs punycode.rs uts46.rs

instant

lib.rs native.rs

ipnetwork

common.rs ipv4.rs ipv6.rs lib.rs

itoa

kernel32

libc

unix

linux_like

linux

arch

generic

gnu

b64

x86_64

align.rs mod.rs not_x32.rs

align.rs mod.rs

align.rs mod.rs

align.rs mod.rs

fixed_width_ints.rs lib.rs macros.rs

libsqlite3_sys

error.rs lib.rs

lock_api

lib.rs mutex.rs remutex.rs rwlock.rs

log

lib.rs macros.rs

matches

memchr

migrations_internals

connection.rs lib.rs migration.rs schema.rs

migrations_macros

embed_migrations.rs lib.rs migrations.rs util.rs

mysqlclient_sys

bindings_macos.rs lib.rs

num_bigint

algorithms.rs bigint.rs biguint.rs lib.rs macros.rs monty.rs

num_integer

average.rs lib.rs roots.rs

num_traits

ops

checked.rs inv.rs mod.rs mul_add.rs overflowing.rs saturating.rs wrapping.rs

bounds.rs cast.rs float.rs identities.rs int.rs lib.rs macros.rs pow.rs real.rs sign.rs

parking_lot

condvar.rs deadlock.rs elision.rs fair_mutex.rs lib.rs mutex.rs once.rs raw_fair_mutex.rs raw_mutex.rs raw_rwlock.rs remutex.rs rwlock.rs util.rs

parking_lot_core

thread_parker

linux.rs mod.rs

lib.rs parking_lot.rs spinwait.rs util.rs word_lock.rs

percent_encoding

pq_sys

proc_macro2

detection.rs fallback.rs lib.rs marker.rs parse.rs wrapper.rs

quickcheck

arbitrary.rs lib.rs tester.rs

quote

ext.rs format.rs ident_fragment.rs lib.rs runtime.rs spanned.rs to_tokens.rs

r2d2

config.rs event.rs extensions.rs lib.rs

regex

regex_syntax

lib.rs literals.rs parser.rs unicode.rs

ryu

buffer

pretty

exponent.rs mantissa.rs mod.rs

common.rs d2s.rs d2s_full_table.rs d2s_intrinsics.rs digit_table.rs f2s.rs f2s_intrinsics.rs lib.rs

scheduled_thread_pool

lib.rs thunk.rs

scopeguard

serde

de

ignored_any.rs impls.rs mod.rs seed.rs utf8.rs value.rs

private

de.rs doc.rs mod.rs ser.rs size_hint.rs

ser

fmt.rs impls.rs impossible.rs mod.rs

integer128.rs lib.rs macros.rs

serde_derive

internals

ast.rs attr.rs case.rs check.rs ctxt.rs mod.rs receiver.rs respan.rs symbol.rs

bound.rs de.rs dummy.rs fragment.rs lib.rs pretend.rs ser.rs try.rs

serde_json

features_check

io

value

de.rs from.rs index.rs mod.rs partial_eq.rs ser.rs

de.rs error.rs iter.rs lib.rs macros.rs map.rs number.rs read.rs ser.rs

smallvec

syn

thread_id

thread_local

time

display.rs duration.rs lib.rs parse.rs sys.rs

tinyvec

array

generated_impl.rs

array.rs arrayvec.rs arrayvec_drain.rs lib.rs slicevec.rs tinyvec.rs

tinyvec_macros

unicode_bidi

char_data

mod.rs tables.rs

deprecated.rs explicit.rs format_chars.rs implicit.rs level.rs lib.rs prepare.rs

unicode_normalization

__test_api.rs decompose.rs lib.rs lookups.rs no_std_prelude.rs normalize.rs perfect_hash.rs quick_check.rs recompose.rs replace.rs stream_safe.rs tables.rs

unicode_xid

lib.rs tables.rs

url

encoding.rs form_urlencoded.rs host.rs lib.rs origin.rs parser.rs path_segments.rs quirks.rs slicing.rs

utf8_ranges

char_utf8.rs lib.rs

uuid

adapter

builder

error.rs mod.rs

parser

error.rs mod.rs

error.rs lib.rs prelude.rs

winapi

use super::methods::LimitDsl;
use dsl::Limit;
use expression::grouped::Grouped;
use expression::subselect::Subselect;
use query_builder::SelectQuery;
use sql_types::{IntoNullable, SingleValue};

/// The `single_value` method
///
/// This trait should not be relied on directly by most apps. Its behavior is
/// provided by [`QueryDsl`]. However, you may need a where clause on this trait
/// to call `single_value` from generic code.
///
/// [`QueryDsl`]: ../trait.QueryDsl.html
pub trait SingleValueDsl {
    /// The type returned by `.single_value`.
    type Output;

    /// See the trait documentation.
    fn single_value(self) -> Self::Output;
}

impl<T, ST> SingleValueDsl for T
where
    Self: SelectQuery<SqlType = ST> + LimitDsl,
    ST: IntoNullable,
    ST::Nullable: SingleValue,
{
    type Output = Grouped<Subselect<Limit<Self>, ST::Nullable>>;

    fn single_value(self) -> Self::Output {
        Grouped(Subselect::new(self.limit(1)))
    }
}