那么检查行是否存在的最佳方法是什么?存在，COUNT或num_rows个? [英] So what IS the best way to check if a row exists? EXISTS, COUNT or num_rows?

问题描述

如果您唯一的目标是检查php (是或否)中是否存在一行，那么最好的方法是什么?

If your only goal is to check if a row exists in php (true or false), what is the best way to do it?

选项1?

$result = mysql_query("SELECT * FROM users WHERE id = '1'");
$num_rows = mysql_num_rows($result);

if ($num_rows == 1) 
    // one user, like it should be.

else 
  // do something else

选项2?

$query = mysql_query("select count(1) from users where id = 1")

if (mysql_result($query, 0) == 1)
    // one user, like it should be.

else 
  // do something else

选项3?

$query = mysql_query("something like SELECT EXISTS( SELECT */1/COUNT(*)/etc. ...)")

if (mysql_result($query, 0) == 1)
    // one user, like it should be.

else 
  // do something else

更好的选项4?

您为它命名.

子问题

• COUNT(*), COUNT(1) or COUNT(id)?

推荐答案

选项3是使用MySQL检查行是否存在的最快方法:

Option 3 is the fastest way to check if a row exists if you are using MySQL:

$query = mysql_query("SELECT EXISTS(SELECT 1 FROM users WHERE id = 1)")

if (mysql_result($query, 0) == 1)
    // one user, like it should be.

else 
  // do something else

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