pub struct MergeUpdateExpr {
    pub update_token: AttachedToken,
    pub assignments: Vec<Assignment>,
    pub update_predicate: Option<Expr>,
    pub delete_predicate: Option<Expr>,
}

UPDATE SET quantity = T.quantity + S.quantity

The UPDATE token that starts the sub-expression.

The update assiment expressions

where_clause for the update (Oralce specific)

delete_clause for the update “delete where” (Oracle specific)