使用具有特定值的php计算mysql中的行数

Question

我有一个表名是tb1

tb1
id zone  pressure
1  India  Yes
2   USA   No
3   UK    Yes
4  India  Yes
5  AUS    No
6   UK    Yes

压力有两种类型的条目，如“是”和“否”，我需要这样的结果

Zone   Pressure
        Yes  No
India    2   0
USA      0   1
UK       1   1
AUS      0   1

到目前为止我的努力......

$result = mysql_query("SELECT Zone FROM Tb1 WHERE Pressure = 'Yes'");
$num_rows = mysql_num_rows($result); echo $num_rows . " \n";

Answer 1

SELECT zone,
       SUM(pressure = 'Yes') AS `Yes`,
       SUM(pressure = 'No') AS `No`
  FROM tb1
 GROUP BY zone

你需要的技巧。这是一个聚合查询。这是一个小提琴。 http://sqlfiddle.com/#!2/54889/2/0

Answer 2

SELECT zone
     , SUM(pressure='yes') yes
     , SUM(pressure='no') no 
  FROM my_table 
 GROUP 
    BY zone;

Answer 3

SELECT Zone,
       SUM(pressure='Yes') as `Yes`,
       SUM(pressure='No') as `No`
FROM Tb1 
GROUP BY Zone;

Answer 4

你可以这样做

select tb1.zone,
sum(tb1.pressure = 'Yes') as Yes,
sum(tb1.pressure = 'No') as No
from tb1
group by tb1.zone