code: static QueryMeta buildDeleteSql(ActiveRecord activeRecord) {
          QueryMeta     queryMeta = new QueryMeta();
          StringBuilder sqlBuf    = new StringBuilder("DELETE FROM " + activeRecord.getTableName());
  
          int[]        pos  = {1};
          List<Object> list = parseWhere(activeRecord, pos, sqlBuf);
  
          if (activeRecord.whereValues.isEmpty()) {
              throw new RuntimeException("Delete operation must take conditions.");
          } else {
              if (sqlBuf.indexOf(Const.SPACE + Const.SQL_WHERE + Const.SPACE) == -1) {
                  sqlBuf.append(Const.SPACE + Const.SQL_WHERE + Const.SPACE);
              }
          }
  
          List<Object> temp = andWhere(activeRecord, pos, sqlBuf);
          if (null != temp) {
              list.addAll(temp);
          }
  
          String sql = sqlBuf.toString();
  
          sql = sql.replace(", WHERE", " WHERE").replace("AND  OR", "OR");
          if (sql.endsWith(Const.SQL_AND + Const.SPACE)) {
              sql = sql.substring(0, sql.length() - 5);
          }
  
          Object[] args = list.toArray();
          queryMeta.setSql(sql);
          queryMeta.setParams(args);
          return queryMeta;
      }
docs: 构造一个删除SQL
  
  @param activeRecord ActiveRecord
  @return 返回QueryMeta对象