public List<String> build() {
    return switch (dialect.getId()) {
      case Oracle.ID -> forOracle(tableName);
      case H2.ID, PostgreSql.ID -> singletonList("drop table if exists " + tableName);
      case MsSql.ID ->
        // "if exists" is supported only since MSSQL 2016.
        singletonList("drop table " + tableName);
      default -> throw new IllegalStateException("Unsupported DB: " + dialect.getId());
    };
  }
@Test
  public void drop_tables_on_h2() {
    assertThat(new DropTableBuilder(new H2(), "issues")
      .build()).containsOnly("drop table if exists issues");
  }