MySQL 查詢、子查詢、distinct、count、

Question

Employees表

名稱。	新的。
沙達布。	是的
阿里。	不
沙達布。	是的

結果

名稱。	新的（是）。	新品(否)
沙達布。	2.	0
阿里。	.	1

如何從Employees表中得到這個結果？ 使用 MySQL。

只需計算New列的Yes和No 。

Answer 1

SELECT DISTINCT
    a.name, 
    coalesce(yes.numbers, 0), 
    coalesce(no.numbers, 0) 
FROM employees AS a
    LEFT JOIN (SELECT name, count(name) AS numbers FROM employees WHERE new = 'Yes' GROUP BY name) AS yes ON (a.name = yes.name)
    LEFT JOIN (SELECT name, count(name) AS numbers FROM employees WHERE new = 'No' GROUP BY name) AS no ON (a.name = no.name)

或使用 SUM 和 IF：

SELECT
    name,
    SUM(IF(new = 'Yes', 1, 0)) as yes_num,
    SUM(IF(new = 'No', 1, 0)) as no_num
FROM employees
GROUP BY name

Answer 2

在這里你可以檢查結果

這是您需要的查詢：

SELECT 
Name,
SUM(CASE WHEN New='Yes' THEN 1 ELSE 0 END) as NEW_Yes,
SUM(CASE WHEN New!='Yes' THEN 1 ELSE 0 END) as NEW_No 
FROM `employees` 
GROUP BY Name