php - Mysql插入数据如果不存在否则显示警告

Question

我需要检查值是否已经存在于表中，如果不存在则插入它，否则我需要显示异常警报

现在我只插入数据而不检查

if(isset($_POST['new_ok'])){$result = mysql_query("INSERT INTO db1 (name) VALUES('".$name."')",$db);}

我试着那样做

if(isset($_POST['new_ok'])){if(mysql_num_rows(mysql_query("SELECT name FROM db1 WHERE name= '$name'");) != 0){$result = mysql_query("INSERT INTO db1 (name) VALUES('".$name."')",$db);}else{echo "wrong";}}

但是mysql_num_rows 总是返回1

Answer 1

试试这个例子

$sq="SELECT * FROM db1 WHERE username='$name'";
 $rsult=mysql_query($sq);      $count=mysql_num_rows ($rsult); 
if($count==1){echo "username already in use"; }

else 
 {//update statement here}