一个查询中有多个计数

Question

此查询不起作用。有人能帮助我吗？

$query = "SELECT 
    COUNT(WHERE Name='george') AS george_total, 
    COUNT(WHERE Name='michael') AS michael_total, 
    COUNT(WHERE Name='mike') AS mike_total 
FROM users WHERE Banned IS NOT '1' AND Active='yes' AND Logins>1 AND Registered_to_forum='1'"; 

$row=mysql_fetch_array($result); 
echo " 
    We found $row['george_total'] people with the name 'George' in our database, 
    $row['michael_total'] with the name Michael 
    and $row['mike_total'] with the name Mike. 
"; 

Answer 1

您可以使用CASE声明，要么COUNT或SUM。

COUNT版本低于。 COUNT只能算作NOT NULL值，所以你可以使用任何非NULL列或常量，而不是1

SELECT 
    COUNT(CASE WHEN Name='george' THEN 1 END) AS george_total, 
    COUNT(CASE WHEN Name='michael' THEN 1 END) AS michael_total, 
    COUNT(CASE WHEN Name='mike' THEN 1 END) AS mike_total /*.... rest of query*/ 

的SUM版本

SELECT 
    SUM(CASE WHEN Name='george' THEN 1 ELSE 0 END) AS george_total, 
    SUM(CASE WHEN Name='michael' THEN 1 ELSE 0 END) AS michael_total, 
    SUM(CASE WHEN Name='mike' THEN 1 ELSE 0 END) AS mike_total /*.... rest 
                    of query*/