Question

我正在尝试从数组中获取数据库中不存在的值或数据。

 public  Cursor checkExistence(){
        Cursor c=null;
        String[] values={"headache","cold"};
        SQLiteDatabase db= getReadableDatabase();
        String query="SELECT * FROM "+TABLE_SYMPTOMS+" WHERE "+COLUMN_SYMP+" IN ("+toArrayRep(values)+")";
        c=db.rawQuery(query,null);
        Log.i("From Cursor","Cursor Count : " + c.getCount());
        if(c.getCount()>0){
            String val= c.getString()
            Log.i("From Cursor","No insertion");
        }else{
            Log.i("From Cursor","Insertion");
        }
        db.close();
        return c;
    }



 public static String toArrayRep(String[] in) {
    StringBuilder result = new StringBuilder();
    for (int i = 0; i < in.length; i++) {
        if (i != 0) {
            result.append(",");
        }
        result.append("'" + in[i] + "'");
    }
    return result.toString();
}

在String values={"headache","cold"}中，头痛存在，但数据库中不存在冷。从上面的代码中，Cursor返回Count=1 count>0，因此我无法插入到表中。我想知道如何独立检查单个数据是否存在，以及是否存在将存在将插入到表中。因此，在这种情况下，“Cold”将能够插入到表中。

Answer 1

如果您使用单个查询来检查所有值，那么您获得的是现有值列表，您仍然需要在原始列表中搜索任何差异。

单独检查每个值更简单：

<div class="container"  >
<br>
<h1><B><font color="red" style= "font-size:70"> Ayoola's Calculator </font>     </B></h1>
<form name="calculator" >
   <input name = "display" placeholder="0" style= "width:254px; height:60px; 
      text-align:right; font-size:30; border-radius:8px; margin:3px"/>
   <br>
   <input name = "answer" placeholder="0" style= "width:254px; height:60px; text-align:right; font-size:30; border-radius:8px; margin:3px"/>
   <br>
   <input type="button" value= "7" name="seven"  onClick="document.calculator.display.value+='7'" style="width:60px; font-size:30; margin:3px"/>
   <input type="button" value= "8" name="eight"  onClick="document.calculator.display.value+='8'" style="width:60px; font-size:30; "/>
   <input type="button" value= "9" name="nine"   onClick="document.calculator.display.value+='9'" style="width:60px; font-size:30; "/>
   <input type="button" value= "*" name="multiply()" onClick="document.calculator.display.value+='*'" style="width:60px;  font-size:30; "/>
   <br>
   <input type="button" value= "4" name="four"  onClick="document.calculator.display.value+='4'" style="width:60px; font-size:30;  margin:3px"/>
   <input type="button" value= "5" name="five"  onClick="document.calculator.display.value+='5'" style="width:60px; font-size:30; "/>
   <input type="button" value= "6" name="six"   onClick="document.calculator.display.value+='6'" style="width:60px; font-size:30; "/>
   <input type="button" value= "-" name="minus()"  onClick="document.calculator.display.value+='-'" style="width:60px; font-size:30; "/>
   <br>
   <input type="button" value= "1" name="one"   onClick="document.calculator.display.value+='1'" style="width:60px; font-size:30;  margin:3px"/>
   <input type="button" value= "2" name="two"   onClick="document.calculator.display.value+='2'" style="width:60px; font-size:30; "/>
   <input type="button" value= "3" name="three" onClick="document.calculator.display.value+='3'" style="width:60px; font-size:30; "/>
   <input type="button" value= "+" name="plus()"  onClick="document.calculator.display.value+='+'" style="width:60px; font-size:30; "/>
   <br>
   <input type="button" value= "." name="point"  onClick="document.calculator.display.value+='.'" style="width:60px; font-size:30;  margin:3px"/>
   <input type="button" value= "0" name="zero"   onClick="document.calculator.display.value+='0'" style="width:60px; font-size:30; "/>
   <input type="button" value= "/" name="divide()"  onClick="document.calculator.display.value+='/'" style="width:60px; font-size:30; "/>
   <input type="button" value= "=" name="equal"  onClick="document.calculator.answer.value=eval(document.calculator.display.value)" style="width:60px;  font-size:30; "/>
   <br>
   <input type="reset" value= "C"   onClick= "clear()" style="width:256px;  font-size:30; margin:3px "/>
</form>

Answer 2

您需要检查光标。 moveToFirst（）

True =在光标中有记录。
错误 =没有记录。

我的代码示例：

return database.query( table.getNameTable(),
                       table.getColumns(),
                       table.getWhereSelectTableScript(),
                       null,
                       table.getGroupBySelectTableScript(),
                       table.getHavingSelectTableScript(),
                       table.getOrderBySelectTableScript(),
                       table.getLimitRecordsSelectTableScript());

查看更多here！

从Array获取特定值，该值在数据库中不存在

2 个答案: