我有此代码：
$sql = "SELECT id FROM videos";
$stmp = $db->prepare($sql);
$stmp->execute();
while ($row = $stmp->fetchAll(PDO::FETCH_ASSOC)) {
$vkey = md5($row['id'] . "video");
$sql = "UPDATE videos SET vkey = :vkey WHERE id = :id";
$stmp = $db->prepare($sql);
$stmp->execute(array(
":vkey" => $vkey,
":id" => $row['id']
));
}
为什么只对第一个选择中的第一个ID执行而不对循环中的所有ID执行？
答案 0 :(得分：3)
您只需执行以下操作即可完全避免所有这些代码：
UPDATE videos SET vkey = MD5(CONCAT(vkey, 'video'))（或者您也可以在后端像PHPMyAdmin $sql = "SELECT id FROM videos";
//no reason to use prepare() because you aren't passing variables.
$stmp = $db->query($sql);
$stmp->execute();
$results = $stmp->fetchAll(PDO::FETCH_ASSOC);
//prepare UPDATE query outside of loop, this way you don't send 2 requests to your database for every row
$stmp = $db->prepare("UPDATE videos SET vkey = :vkey WHERE id = :id");
foreach($results as $result) {
$vkey = md5($result['id']."video");
$stmp->execute(
array(
":vkey" => $vkey,
":id" => $result['id']
)
);
}
这样进行查询）
但是，如果出于某种原因要遍历数据库，则可以执行以下操作：
$stmp->rowCount()此外，通常最好检查循环中的返回值以确保没有错误，您可以使用#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int ticket,tnotran,tran;
char pass[40],desti[2],cla,destina[20],clana[20];
float tfare,cfare,nfare,gtnfare;
int main(int argc, char *argv[]) {
printf("\n\n\t\tTicket NO.: ");
scanf("%d",&ticket);
while (ticket != 0){
head();
con();
system("pause");
system("cls");
netcomp();
out();
system("pause");
system("cls");
printf("\n\n\t\tTicket NO.: ");
scanf("%d",&ticket);
}
printf("\n\n\t\tTotal No. of Transactions: %d", tran);
printf("\n\n\t\tGrand Total of Net Fare: %f", gtnfare);
}
head(){
printf("\n\t\tPassenger's Name: ");
scanf("%s",&pass);
printf("\n\t\tDestination Code: ");
scanf("%s",&desti);
printf("\n\t\tClass Code: ");
scanf("%s",&cla);
}
con(){
if(strcpy(desti, "HK")||strcpy(desti, "hk")){
tfare= 8500;
printf("\n\t\tTicket Fare: %.2f", tfare);
strcpy(destina,"Hong Kong");
}
else if(strcpy(desti, "BK")||strcpy(desti, "bk")){
tfare= 7500;
printf("\n\t\tTicket Fare: %.2f", tfare);
strcpy(destina,"Bangkok");
}
else if(strcpy(desti, "KL")||strcpy(desti, "kl")){
tfare= 7900;
printf("\n\t\tTicket Fare: %.2f", tfare);
strcpy(destina,"Kualala Lumpur");
}
else if(strcpy(desti, "TP")||strcpy(desti, "tp")){
tfare= 8300;
printf("\n\t\tTicket Fare: %.2f", tfare);
strcpy(destina,"Taipe");
}
else{
printf("\n\t\tInvalid Input");
tfare=0;
}
if(cla== 'E'|| cla=='e'){
cfare= 1500;
printf("\n\t\tClass Fare: %.2f", cfare);
strcpy(clana,"Economy");
}
else if(cla== 'T'|| cla=='t'){
cfare= 2500;
printf("\n\t\tClass Fare: %.2f", cfare);
strcpy(clana,"Tourist");
}
else if(cla== 'F'|| cla=='f'){
cfare= 3500;
printf("\n\t\tClass Fare: %.2f", cfare);
strcpy(clana,"First Class");
}
}
netcomp(){
nfare = tfare+ cfare;
gtnfare +=nfare;
tran += 1;
}
out(){
printf("\n\n\t\tTicket NO.: %d", ticket);
printf("\n\t\tPassenger's Name: %s", pass);
printf("\n\t\tDestination: %s", destina);
printf("\n\t\tClass: %s", clana);
printf("\n\t\tNet Fare: %f", nfare);
}
之类的方法来检查是否有任何行受到影响。< / p>