交叉表在MySQL

Question

我有這個數據

| car_name | year | price 
| Honda | 2011 | 123 
| Honda | 2012 | 124 
| Suzuki | 2011 | 1234 
| Suzuki | 2012 | 1235 

IM要去如何變成

| car_name | 2011 | 2012 | 
| Honda | 123 | 124 
| Suzuki | 1234 | 1235 

這個請大家幫我

Answer 1

在MySQL中，您可以執行以下操作：

SELECT car_name, 
    max(case when year = '2011' then price ELSE 0 END) as `2011`, 
    max(case when year = '2012' then price ELSE 0 END) as `2012` 
FROM t 
GROUP BY car_name 

見SQL Fiddle with a Demo

Answer 2

在PHP中，這裏是你的答案：

$sql = "SELECT DISTINCT `year` FROM `table`"; 
$result = mysql_query($sql); 


$sql2_select = "SELECT t1.`car_name`"; 
$sql2_from = "FROM `table` t1"; 

$i = 2; 
while($row = mysql_fetch_row($result)) { 
    $year = $row[0]; 

    $sql2_select .= ", t{$i}.`price` AS `$year`" 

    $sql_from .= " LEFT JOIN (SELECT `car_name`, `price` WHERE `year` = '$year') AS t{$i}"; 
    $sql_from .= " ON t1.`car_name` = t2.`car_name`"; 

    $i++; 
} 

$sql2 = $sql2_select . ' ' . $sql2_from . ' ' . "GROUP BY t1.car_name"; 

$result = mysql_query($sql2); 

Answer 3

一種方式做在MySQL交叉表與子查詢：

select car_name, 
(select price from t t2 where t2.car_name = t1.car_name and year = 2011) as '2011', 
(select price from t t2 where t2.car_name = t1.car_name and year = 2012) as '2012' 
from t t1 
group by car_name 

SQL Fiddle

如果每車每年，那麼總和多個記錄（價錢）。