拥有 2 个产品的员工列表

Question

有人可以帮忙吗？

我有表员工。我想找出拥有 2 个产品（P1，P2）的员工名单。

Emp_id    Prd_id
  E1         P1
  E1         P2
  E2         P1
  E2         P2
  E2         P3
  E3         P1
  E3         P3
  E4         P1
  E4         P2

所以，我想输出为

Emp_id
  E1
  E4

Answer 1

SELECT emp_id
FROM employee
GROUP BY emp_id
HAVING COUNT(CASE WHEN prd_id 'p1' THEN 1 END) > 0 -- p1 exists
   AND COUNT(CASE WHEN prd_id 'p2' THEN 1 END) > 0 -- p2 exists
   AND COUNT(CASE WHEN prd_id NOT IN ('p1', 'p2') THEN 1 END) = 0 -- but not other

更容易扩展到更多的产品：

SELECT emp_id
FROM 
 ( -- get a unique list first
   SELECT DISTINCT emp_id, prd_id
   FROM employee
 ) AS dt
GROUP BY emp_id
HAVING SUM(CASE WHEN prd_id IN ('p1', 'p2') THEN 1 ELSE -1 END) = 2

Answer 2

如果要求查找拥有任意两种产品的员工，您可以使用having 条件来统计他们：

SELECT   emp_id
FROM     employees
GROUP BY emp_id
HAVING   COUNT(*) = 2

如果这些产品必须是 p1 和 p2，您可以在其上添加另一个条件：

SELECT   emp_id
FROM     employees
GROUP BY emp_id
HAVING   COUNT(*) = 2 AND
         COUNT(CASE WHEN prd_id IN ('p1', 'p2') THEN 1 END) = 2