void appendMergeClause(StringBuilder sb) {
        sb.append("MERGE INTO ");
        dialect.quoteIdentifier(sb, jdbcTable.getExternalNameList());
        sb.append(' ');
        appendFieldNames(sb, jdbcTable.dbFieldNames());
    }
@Test
    void appendMergeClause() {
        H2UpsertQueryBuilder builder = new H2UpsertQueryBuilder(table, dialect);
        StringBuilder sb = new StringBuilder();
        builder.appendMergeClause(sb);

        String mergeClause = sb.toString();
        assertThat(mergeClause).isEqualTo("MERGE INTO \"table1\" (\"field1\",\"field2\")");
    }