PHP查询数据库用FOR循环问题

这当然是不行的了,上面的告诉你的也是错误的，因为原因在于你循环的时候进行了数据库的查询，所以每次都是新的数据，指针当然要从第一条开始了。

所以不是你的循环的错误，而是你数据库查询代码位置的错误

要这样写

$num=mysql_query("select

*

from

china_city

where

parentid=0")

$n=

mysql_num_rows

($num)

for($i=1$i<=$n$i++){

${"row".$i}=mysql_fetch_array($num)

echo

$i."

".${"row".$i}['city']."

"

}

一般都是用foreach或while写的

foreach(mysql_fetch_array($num)

as

$key=>$value){}

while($row

=mysql_fetch_array($num)){}

for (Device dev : list) {

String dmi = dev.getDeviceModelId()

if (StringUtils.isBlank(dmi)){

continue

}

DeviceModel dm = this.deviceModelManager.get(dmi)//查询数据库

dev.setDeviceModel(dm)

}

代码块二：

List<String>deviceModelIdList = new ArrayList<String>()

for (Device dev : list) {

String dmi = dev.getDeviceModelId()

if (StringUtils.isBlank(dmi)){

continue

}

deviceModelIdList.add(dmi)

}

List<DeviceModel>deviceModelList = this.deviceModelManager.find(new NameValuePair("id", MatchMode.IN, deviceModelIdList))//查询数据库

for (Device dev : list) {

for(DeviceModel model : deviceModelList){

if(model.getId().equals(dev.getDeviceModelId())){

dev.setDeviceModel(model)

}

}

}

---