Struct Placeholder 

pub struct Placeholder {
    pub name: Option<&'static str>,
}

SQL building blocks. A SQL parameter placeholder.

Placeholders store a semantic name for parameter binding. The actual SQL syntax ($1, ?, :name) is determined by the Dialect at render time.

Fields

name: Option<&'static str>

The semantic name of the parameter (used for binding by name).

Implementations

impl Placeholder

pub const fn named(name: &'static str) -> Placeholder

Creates a named placeholder.

The name is used for binding; rendering is dialect-specific:

• PostgreSQL: $1, $2, … (positional, name ignored in SQL)
• SQLite: :name for named placeholders
• MySQL: ? (positional, name ignored in SQL)

pub const fn anonymous() -> Placeholder

Creates an anonymous placeholder (no name).

pub const fn typed<T>(name: &'static str) -> TypedPlaceholder<T>

where T: DataType,

Creates a typed named placeholder.

pub const fn typed_nullable<T>(name: &'static str) -> TypedPlaceholder<T, Null>

where T: DataType,

Creates a typed nullable named placeholder.

Trait Implementations

impl Clone for Placeholder

fn clone(&self) -> Placeholder

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Copy for Placeholder

impl Debug for Placeholder

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

Formats the value using the given formatter.

impl Default for Placeholder

fn default() -> Placeholder

Returns the “default value” for a type.

impl Display for Placeholder

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

Debug display: ? for anonymous or :name for named. Note: actual SQL rendering uses dialect-specific placeholders via SQL::write_to.

impl Eq for Placeholder

impl<'a, V> Expr<'a, V> for Placeholder

where V: SQLParam + 'a,

type SQLType = Placeholder

The SQL data type this expression evaluates to.

type Nullable = NonNull

Whether this expression can be NULL.

type Aggregate = Scalar

Whether this is an aggregate (COUNT, SUM) or scalar expression.

fn to_expr_sql(&self) -> SQL<'a, V>

Render this value as a scalar expression by reference.

fn into_expr_sql(self) -> SQL<'a, V>

where Self: Sized,

Render this value as a scalar expression, consuming it when useful.

fn to_condition_sql(&self) -> Option<SQL<'a, V>>

Render this value as one element of a ConditionList.

fn into_condition_sql(self) -> Option<SQL<'a, V>>

where Self: Sized,

Consuming counterpart of Expr::to_condition_sql.

impl<V> From<Placeholder> for Param<'_, V>

where V: SQLParam,

fn from(value: Placeholder) -> Param<'_, V>

Converts to this type from the input type.

impl<T, N> From<TypedPlaceholder<T, N>> for Placeholder

where T: DataType, N: Nullability,

fn from(value: TypedPlaceholder<T, N>) -> Placeholder

Converts to this type from the input type.

impl Hash for Placeholder

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'a, V> PaginationArg<'a, V> for Placeholder

where V: SQLParam + 'a,

fn into_pagination_sql(self) -> SQL<'a, V>

impl PartialEq for Placeholder

fn eq(&self, other: &Placeholder) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Placeholder

impl<'a, V> ToSQL<'a, V> for Placeholder

where V: SQLParam + 'a,

fn to_sql(&self) -> SQL<'a, V>

fn into_sql(self) -> SQL<'a, V>

where Self: Sized,

Consume self and return SQL without cloning. Default delegates to to_sql() (which clones). Types that own their SQL (like SQL and SQLExpr) override this to avoid the clone.