pub struct MergeClause {
    pub when_token: AttachedToken,
    pub clause_kind: MergeClauseKind,
    pub predicate: Option<Expr>,
    pub action: MergeAction,
}

WHEN NOT MATCHED BY SOURCE AND product LIKE '%washer%' THEN DELETE

The WHEN token that starts the sub-expression.

The type of WHEN clause.

An optional predicate to further restrict the clause.

The action to perform when the clause is matched.