Question

可能重复：
Is there a way to make this SQL more efficient?

考虑以下表格：

department：

deptid (type: INT)
deptname (type: TEXT)
hours (type: INT)
active (type: BIT)

employee：

empid (type: INT)
empname (type: TEXT)
deptid (type: INT)
designation (type: TEXT)
salary (type: INT)

编写查询以返回属于人数为4或更多的部门的员工的empname和deptname列。记录应按empname的字母顺序返回。

我的解决方案如下。

SELECT e.empname,d.deptname
FROM employee e,department d
WHERE e.deptid=d.deptid
      AND d.deptid
         IN
(
SELECT deptid
FROM employee
GROUP BY deptid
HAVING COUNT(*)>=4
)
ORDER BY e.empname;

Answer 1

您的问题的答案可以在this link上找到。

SELECT employee.empname, department.deptname
FROM employee
INNER JOIN department ON employee.deptid = department.deptid
WHERE employee.deptid IN 
(
  SELECT employee.deptid
  FROM employee
  GROUP BY employee.deptid
  HAVING COUNT(employee.deptid) >= 4
)
ORDER BY employee.empname ASC;

编辑：如果您希望我在此解决方案中解释任何内容，请随时提出。：）

我的SQL查询不起作用

1 个答案: