code: private String convertToString(Object newValue, Database database) {
      String sqlString;
      if (newValue == null || newValue.toString().equals("") || newValue.toString().equalsIgnoreCase("NULL")) {
        sqlString = "NULL::INTEGER";
      } else if (newValue instanceof String && !looksLikeFunctionCall(((String) newValue), database)) {
        sqlString = "'" + database.escapeStringForDatabase(newValue.toString()) + "'";
      } else if (newValue instanceof Date) {
        sqlString = database.getDateLiteral(((Date) newValue));
      } else if (newValue instanceof Boolean) {
        if (((Boolean) newValue)) {
          sqlString = DataTypeFactory.getInstance().getTrueBooleanValue(database);
        } else {
          sqlString = DataTypeFactory.getInstance().getFalseBooleanValue(database);
        }
      } else {
        sqlString = newValue.toString();
      }
      return sqlString;
    }
docs: Copied and modified from liquibase.sqlgenerator.core.InsertOrUpdateGeneratorMySQL