PHP query database to meet the conditions of the number of records (two implementation methods) _php instance

When you need to output the number of Web site users, or before you insert data to determine whether there are duplicate records, you need to get the number of records of the MySQL query to meet the conditions.
The first method: Query time Direct statistics

Copy Code code as follows:

$sql = "SELECT count (*) as Count from TABLE WHERE id= ' $id '";
$result =mysql_fetch_array (mysql_query ($sql));
$count = $result [' count '];

The second method: First out, after the statistics

Copy Code code as follows:

$sql = "SELECT * from TABLE WHERE id= ' $id '";
$result =mysql_fetch_array (mysql_query ($sql));
$count =count ($result);//or $count=mysql_num_rows ($result);

However, the direct use of MySQL's count (*) in the large amount of data, the advantage of efficiency is very significant, because the latter requires two times, so it is best to use the former for data bar count.