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Multiple methods for mysqli to process query result sets in PHP

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Release: 2019-04-18 11:48:27
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Recently, I looked up information that I didn’t quite understand about several methods of PHP query mysql processing result sets, so I compiled them here (related recommendations: mysql tutorial)

Php uses the mysqli_result class to process the result set in the following ways

fetch_all() grab Takes all result rows and returns the result set as associative data, a numerically indexed array, or both.
fetch_array() Fetch as an associative array, a numeric index array, or both Get a row of results.
fetch_object() Returns the current row of the result set as an object.
fetch_row() Returns a row of results in the form of an enumeration array
fetch_assoc() Fetch a row of results in an associative array.
fetch_field_direct() Returns the metadata of a single field in the result set as an object.
fetch_field() Returns the column information in the result set as an object.
fetch_fields() Returns the column information representing the result set in an object array .

fetch_all (Get all rows from the result set as an associative array)

  $sql="select * from user";
  $result=$link->query($sql);
  $row=$result->fetch_all(MYSQLI_BOTH);//参数MYSQL_ASSOC、MYSQLI_NUM、MYSQLI_BOTH规定产生数组类型
  $n=0;
  while($n<mysqli_num_rows($result)){
   echo "ID:".$row[$n]["id"]."用户名:".$row[$n]["name"]."密码:".$row[$n]["password"]."<br />";
   $n++;
  }
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fetch_array (Fetch a row of results as an associative array, a numeric index array, or both)

 $sql="select * from user";
        $result=$link->query($sql);
        while($row=$result->fetch_array()){
            echo "ID:".$row["id"]."用户名:".$row[1]."密码:".$row["password"]."<br />";
        }
//fetch_array方法不再有结果时返回返回NULL
//其返回结果可以是关联数组也可以是数值数组索引,故$row["id"]、$row[1]都可以
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fetch_object (Returns the current row of the result set as an object)

   $sql="select * from user";
        $result=$link->query($sql);
        while($row=$result->fetch_object()){
            echo "ID:".$row->id."用户名:".$row->name."密码:".$row->password."<br />";
        }
//如果无更多的行则返回NULL
//返回的结果是对象,要以对象的方式调用
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fetch_row (Return a row of results in the form of an enumeration array)

  $sql="select * from user";
        $result=$link->query($sql);
        while($row=$result->fetch_row()){
            echo "ID:".$row[0]."用户名:".$row[1]."密码:".$row[2]."<br />";
        }
//无更多行时返回NULL
//以数值下标调用数组,a[0]正确、a["id"]则不
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fetch_assoc (Fetch a row of results in an associative array)

 $sql="select * from user";
        $result=$link->query($sql);
        while($row=$result->fetch_assoc()){
            echo "ID:".$row["id"]."用户名:".$row["name"]."密码:".$row["password"]."<br />";
        }
//无更多行时返回NULL
//以关联索引访问数组,a["id"]正确、a[0]则不
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fetch_field_direct (Returns the metadata of a single field in the result set as an object and is a single column Information)

$sql="select * from user";
        $result=$link->query($sql);
        $n=0;
        while(1){
            if(!$row=$result->fetch_field_direct($n++)) break;
            echo "列名:".$row->name."所在表:".$row->table."数据类型:".$row->type."<br />";
        }
//fetch_field_direct($n)只返回单个列,所以得不断调用该方法,没有该列时返回false
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fetch_field ( Return the column information in the result set as an object)

       $sql="select * from user";
        $result=$link->query($sql);
        while($row=$result->fetch_field()){
            echo "列名:".$row->name."所在表:".$row->table."数据类型:".$row->type."<br />";
        }
//该方法检索所有的列
//以对象方式返回列信息
//返回对象属性如:name - 列名,table - 该列所在的表名,type - 该列的类型,等
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fetch_fields (Return column information representing the result set as an object array)

    $sql="select * from user";
        $result=$link->query($sql);
        $row=$result->fetch_fields();
        foreach($row as $val){
            echo "列名:".$val->name."所在表:".$val->table."数据类型:".$val->type."<br />";
        }
//该方法功能与目的fetch_field一样
//不一样的是该方法返回一个对象数组(如:echo $row[0]->name;输出第一列的名字),而不是一次检索一列
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Another: mysqli_result class has other Method

field_tell() Returns the position of the field pointer
data_seek() Adjust the result pointer to an arbitrary row in the result set
num_fields() Returns the number of fields (number of columns) in the result set
field_seek() Adjust the field pointer to the specific field start position
free() Release the memory associated with a result set
fetch_lengths() Returns the column length of the current row in the result set
num_rows() Returns the number of rows in the result set

refer to Information: php manual (http://php.net/manual/zh/class.mysqli-result.php)

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