Struct CaseBuilder 

pub struct CaseBuilder<'a, V: SQLParam, T: DataType, N: Nullability, A: AggregateKind, S = ()> { /* private fields */ }

A CASE builder with at least one branch.

T is the result type set by the first branch and N the nullability of the results so far. S records the tables read so far: WHEN conditions are only scope-checked (a NULL condition falls through to the next branch), while THEN results can make the result NULL.

Implementations

impl<'a, V, T, N, A, S> CaseBuilder<'a, V, T, N, A, S>

where V: SQLParam + 'a, T: DataType, N: Nullability, A: AggregateKind,

pub fn when<C, R>( self, condition: C, result: R, ) -> CaseBuilder<'a, V, T, <N as Nullability>::Or<R::Nullable>, <<A as AggregateKind>::Or<C::Aggregate> as AggregateKind>::Or<R::Aggregate>, (S, (ScopeOnly<C::Sources>, R::Sources))>

where C: Expr<'a, V>, R: Expr<'a, V>, C::SQLType: BooleanLike, T: Compatible<R::SQLType>, N: Nullability, R::Nullable: Nullability, A: AggregateKind, C::Aggregate: AggregateKind, R::Aggregate: AggregateKind,

Adds another WHEN condition THEN result branch.

condition must be boolean and result must have a type compatible with the first branch. The result becomes nullable if this branch’s result is.

pub fn end(self) -> SQLExpr<'a, V, T, Null, A, S>

Finishes the expression without ELSE (... END).

Rows that match no branch give NULL, so the result is always nullable.

Examples

let label = case().when(users.active, "active").end();
assert_eq!(label.sql(), r#"CASE WHEN "users"."active" THEN ? END"#);

pub fn else<D>( self, default: D, ) -> SQLExpr<'a, V, T, <N as Nullability>::Or<D::Nullable>, <A as AggregateKind>::Or<D::Aggregate>, (S, D::Sources)>

where D: Expr<'a, V>, T: Compatible<D::SQLType>, N: Nullability, D::Nullable: Nullability, A: AggregateKind, D::Aggregate: AggregateKind,

Finishes the expression with a default (... ELSE default END).

default must have a type compatible with the first branch. The result is nullable if any branch result or the default is.

Examples

let label = case().when(users.active, "active").r#else("inactive");
assert_eq!(label.sql(), r#"CASE WHEN "users"."active" THEN ? ELSE ? END"#);