mysql使用相同编号的名称计数

Question

我的Mysql表看起来像这样

Field A         Field B
Red             yes
Blue                yes
Red             no
Green           no
Blue                yes
Blue                yes
Green           no
Green           yes
Red             no

我希望结果是：

Red     1
Blue        3
Green   1

任何帮助

Answer 1

条件计数

SELECT FieldA, COUNT( CASE WHEN FieldB = 'Yes' THEN 1 END)
FROM YourTable
GROUP BY FieldA

Answer 2

SELECT FieldA, count(FieldA)
FROM table
WHERE table.FieldB = "yes"
GROUP BY FieldA