SQL Distinct Group by

Question

SQL：按国家/地区分组算，非常简单，但我迷路了 我有我的Table1

Country    | Optin    | 
--------------------------
USA        | 1        |
USA        | 1        |      
GERMANY    | 0        |      
USA        | 1        |          
GERMANY    | 1        |         
JAPON      | 1        |  

我想要返回此表，我只想按国家/地区计算optin part = 1

Country    | Optin    | 
--------------------------
USA        | 3        |
GERMANY    | 1        |
JAPON      | 1        |  


SELECT *
FROM Table1
WHERE Optin = 1
GROUP BY Country

Answer 1

  

我只想按国家/地区计算optin part = 1

COUNT使用SUM（或optin，因为所有GROUP BY country返回= 1）：

SELECT Country, COUNT(optin) 
FROM table1
WHERE optin = 1
GROUP BY country;

SQL Fiddle Demo

Answer 2

SELECT  Country, SUM(CASE WHEN Optin = 1 THEN 1 ELSE 0 END) totalOptin
FROM    TableName
GROUP   BY Country

• SQLFiddle Demo