Function substr 

pub fn substr<'a, V, E, S, L>(
    expr: E,
    start: S,
    len: L,
) -> SQLExpr<'a, V, <V::DialectMarker as DialectTypes>::Text, <<E::Nullable as NullOr<S::Nullable>>::Output as NullOr<L::Nullable>>::Output, <<E::Aggregate as AggOr<S::Aggregate>>::Output as AggOr<L::Aggregate>>::Output>
where
    V: SQLParam + 'a,
    E: Expr<'a, V>,
    E::SQLType: Textual,
    S: Expr<'a, V>,
    S::SQLType: Integral,
    S::Nullable: Nullability,
    S::Aggregate: AggregateKind,
    L: Expr<'a, V>,
    L::SQLType: Integral,
    L::Nullable: Nullability,
    L::Aggregate: AggregateKind,
    E::Nullable: NullOr<S::Nullable>,
    <E::Nullable as NullOr<S::Nullable>>::Output: NullOr<L::Nullable>,
    E::Aggregate: AggOr<S::Aggregate>,
    <E::Aggregate as AggOr<S::Aggregate>>::Output: AggOr<L::Aggregate>,

SUBSTR - extracts a substring from a string.

Extracts len characters starting at position start (1-indexed). The result is nullable when any argument is nullable.

Example

use drizzle_core::expr::substr;

// SELECT SUBSTR(users.name, 1, 3) -- first 3 characters
let prefix = substr(users.name, 1, 3);