Mysql 有条件计数
我有一个针对不同国家的不同值的表，例如： id| country | =================== 1 | Argelia | 2 | USA | 1 | China | 1 | Italy | 1 | Italy | 1 | USA | 4 | USA | 1 | Argelia | id |国家| =================== 1 |阿格里亚| 2 |美国| 1 |中国| 1 |意大利| 1 |意大利| 1 |美国| 4 |美国| 1 |阿格里亚| 我只对一个国家的计数和总计数感兴趣，但我很难提出一个查询来完成它。此id 1查询的结果将是： id| value_in_Italy | total ========================== 1 | 2 | 6 id |意大利价值|总计 ========================== 1 | 2 | 6Mysql 有条件计数,mysql,Mysql,我有一个针对不同国家的不同值的表，例如： id| country | =================== 1 | Argelia | 2 | USA | 1 | China | 1 | Italy | 1 | Italy | 1 | USA | 4 | USA | 1 | Argelia | id |国家| =================== 1 |阿格里亚| 2 |美国| 1 |中国| 1 |意大利| 1 |意大利| 1 |美国|
如你所见，我得到了意大利的价值，以及总价值。什么样的查询会为类似的表生成如上所示的行？下面是加载的示例数据
SELECT A.ID,B.value_in_Italy,(SELECT COUNT(DISTINCT Country) AS total FROM YOURTABLE) AS total
FROM YOURTABLE A,
(SELECT Country,COUNT(*) AS value_in_Italy
FROM YOURTABLE
WHERE COUNTRY='Italy'
GROUP BY Country) B
WHERE A.Country=B.Country
mysql> drop database if exists luqita;
Query OK, 1 row affected (0.03 sec)
mysql> create database luqita;
Query OK, 1 row affected (0.01 sec)
mysql> use luqita
Database changed
mysql> create table countrydata
-> (
-> id int not null,
-> country varchar(32),
-> value int not null
-> );
Query OK, 0 rows affected (0.10 sec)
mysql> insert into countrydata (id,country) values
-> (1,'Argelia' ),
-> (2,'USA' ),
-> (1,'China' ),
-> (1,'Italy' ),
-> (1,'Italy' ),
-> (1,'USA' ),
-> (4,'USA' ),
-> (1,'Argelia' );
Query OK, 8 rows affected, 1 warning (0.06 sec)
Records: 8 Duplicates: 0 Warnings: 1
mysql> select * from countrydata;
+----+---------+-------+
| id | country | value |
+----+---------+-------+
| 1 | Argelia | 0 |
| 2 | USA | 0 |
| 1 | China | 0 |
| 1 | Italy | 0 |
| 1 | Italy | 0 |
| 1 | USA | 0 |
| 4 | USA | 0 |
| 1 | Argelia | 0 |
+----+---------+-------+
8 rows in set (0.00 sec)
mysql>
select id,SUM(IF(country='Italy',1,0)) italy_count,COUNT(IF(id=1,1,0)) id_count
from countrydata WHERE id=1;
mysql> select id,SUM(IF(country='Italy',1,0)) italy_count,COUNT(IF(id=1,1,0)) id_count
-> from countrydata WHERE id=1;
+----+-------------+----------+
| id | italy_count | id_count |
+----+-------------+----------+
| 1 | 2 | 6 |
+----+-------------+----------+
1 row in set (0.00 sec)
mysql>
select B.*,
SUM(IF(A.country=B.country,1,0)) country_count,
SUM(IF(B.id=A.id,1,0)) id_count
from
countrydata A,
(select distinct id,country from countrydata) B
group by B.id,B.country;
mysql> select B.*,
-> SUM(IF(A.country=B.country,1,0)) country_count,
-> SUM(IF(B.id=A.id,1,0)) id_count
-> from
-> countrydata A,
-> (select distinct id,country from countrydata) B
-> group by B.id,B.country;
+----+---------+---------------+----------+
| id | country | country_count | id_count |
+----+---------+---------------+----------+
| 1 | Argelia | 2 | 6 |
| 1 | China | 1 | 6 |
| 1 | Italy | 2 | 6 |
| 1 | USA | 3 | 6 |
| 2 | USA | 3 | 1 |
| 4 | USA | 3 | 1 |
+----+---------+---------------+----------+
6 rows in set (0.00 sec)
mysql>
下面是加载的示例数据
mysql> drop database if exists luqita;
Query OK, 1 row affected (0.03 sec)
mysql> create database luqita;
Query OK, 1 row affected (0.01 sec)
mysql> use luqita
Database changed
mysql> create table countrydata
-> (
-> id int not null,
-> country varchar(32),
-> value int not null
-> );
Query OK, 0 rows affected (0.10 sec)
mysql> insert into countrydata (id,country) values
-> (1,'Argelia' ),
-> (2,'USA' ),
-> (1,'China' ),
-> (1,'Italy' ),
-> (1,'Italy' ),
-> (1,'USA' ),
-> (4,'USA' ),
-> (1,'Argelia' );
Query OK, 8 rows affected, 1 warning (0.06 sec)
Records: 8 Duplicates: 0 Warnings: 1
mysql> select * from countrydata;
+----+---------+-------+
| id | country | value |
+----+---------+-------+
| 1 | Argelia | 0 |
| 2 | USA | 0 |
| 1 | China | 0 |
| 1 | Italy | 0 |
| 1 | Italy | 0 |
| 1 | USA | 0 |
| 4 | USA | 0 |
| 1 | Argelia | 0 |
+----+---------+-------+
8 rows in set (0.00 sec)
mysql>
select id,SUM(IF(country='Italy',1,0)) italy_count,COUNT(IF(id=1,1,0)) id_count
from countrydata WHERE id=1;
mysql> select id,SUM(IF(country='Italy',1,0)) italy_count,COUNT(IF(id=1,1,0)) id_count
-> from countrydata WHERE id=1;
+----+-------------+----------+
| id | italy_count | id_count |
+----+-------------+----------+
| 1 | 2 | 6 |
+----+-------------+----------+
1 row in set (0.00 sec)
mysql>
select B.*,
SUM(IF(A.country=B.country,1,0)) country_count,
SUM(IF(B.id=A.id,1,0)) id_count
from
countrydata A,
(select distinct id,country from countrydata) B
group by B.id,B.country;
mysql> select B.*,
-> SUM(IF(A.country=B.country,1,0)) country_count,
-> SUM(IF(B.id=A.id,1,0)) id_count
-> from
-> countrydata A,
-> (select distinct id,country from countrydata) B
-> group by B.id,B.country;
+----+---------+---------------+----------+
| id | country | country_count | id_count |
+----+---------+---------------+----------+
| 1 | Argelia | 2 | 6 |
| 1 | China | 1 | 6 |
| 1 | Italy | 2 | 6 |
| 1 | USA | 3 | 6 |
| 2 | USA | 3 | 1 |
| 4 | USA | 3 | 1 |
+----+---------+---------------+----------+
6 rows in set (0.00 sec)
mysql>
我能想到的MySQL上最简单的查询是：
select id, sum(country = 'Italy') values_in_Italy, count(*) Total from t
where id = 1
MySQL不会强制您按id分组，因为它将不确定地获取一个id，但是
whereselect id, sum(country = 'Italy') values_in_Italy, count(*) Total from t
where id = 1
whereselect 1 id, sum(country = 'Italy') values_in_Italy, count(*) Total from t
select 1 id, sum(country = 'Italy') values_in_Italy, count(*) Total from t
你是如何创建格式良好的表格的？@I_uu：检查我的个人资料，我总是保留一些很酷的链接：）@I_uu：按下我帖子下方的“编辑”按钮，你就可以复制代码了。你是如何创建格式良好的表格的？@I__;：检查我的个人资料，我总是保留一些很酷的链接：）@I_u;：按我帖子下面的“编辑”按钮，你可以复制代码。我希望这有助于你的请求。我没有mysql来测试它。我希望这有助于你的请求。我没有mysql来测试它。只有在有行的情况下，你如何添加子句？例如，如果我没有'where id=1'子句，那么结果中只会显示id 1（因为其他的没有意大利计数），对不起，我不太明白这个问题。要在任何查询中仅显示意大利行，您应该使用此
where country='意大利语'where country='意大利语'