检查表中是否已存在数据，或检查表是否为空

4 回答

• 1

  SELECT COUNT(*) FROM `tableName`;
  

  如果结果为0则表为空;）

  回复于 2024-04-20T02:47:32+08:00
• 2

  精炼的查询

  SELECT COUNT（*）FROM TABLE WHERE ROWNUM = 1

  回复于 2024-04-20T02:47:32+08:00
• 1

  另请阅读DatabaseUtils .

  /**
   * checks database if a column has a value in the table
   *
   * @param db
   * @param tableName
   * @param column
   * @param value
   * @param rowid to check against and skip if necessary
   * @return boolean
   */
  public static boolean ExistsWithName(SQLiteDatabase db, String tableName, String column,
          String value, Long rowid) {
      String sql = String.format("select 1 from %s where %s = '%s'", tableName, column, value);
      if (rowid != null) {
          sql += " and _id != " + rowid;
      }
      Cursor c = null;
      Boolean ret = false;
      try {
          c = db.rawQuery(sql, null);
          if (c != null) {
              if (c.moveToFirst()) {
                  ret = (c.getCount() > 0);
              } else {
                  ret = false;
              }
          }
      } catch (Exception e) {
          Log.v(tableName, e.getMessage(), e);
          e.printStackTrace();
      } finally {
          if (c != null)
              c.close();
      }
      return ret;
  }
  

  回复于 2024-04-20T02:47:32+08:00
• 1

  试试这个，

  public int getTableCount(String tableName) {
  
      int totalCount= 0;
  
      Cursor cur = mDb.rawQuery("SELECT COUNT(*) as count FROM " + tableName , null);
  
      if (cur != null) {
          cur.moveToFirst();
      }
  
      if (cur.moveToFirst()){
          do{
              totalCount = cur.getInt(cur.getColumnIndex("count"));
          }while(cur.moveToNext());
      }
      cur.close();
  
      return totalCount;
  }
  

  其中“mDb” - > SQLiteDatabase对象

  回复于 2024-04-20T02:47:32+08:00