@Override
    public <T> SQLMergeClause setNull(Path<T> path) {
        columns.add(path);
        values.add(Null.CONSTANT);
        return this;
    }
Set the keys to be used in the MERGE clause

@param paths keys
@return the current object
querydsl-sql/src/main/java/com/querydsl/sql/dml/SQLMergeClause.java