public List<String> build() {
    if (columnDefs.isEmpty()) {
      throw new IllegalStateException("No column has been defined");
    }
    switch (dialect.getId()) {
      case PostgreSql.ID:
        return createPostgresQuery();
      case Oracle.ID:
        return createOracleQuery();
      default:
        return createMsSqlAndH2Queries();
    }
  }
@Test
  public void fail_with_ISE_if_no_column() {
    assertThatThrownBy(() -> new AlterColumnsBuilder(new H2(), TABLE_NAME).build())
      .isInstanceOf(IllegalStateException.class)
      .hasMessage("No column has been defined");
  }