Mysql中having与where的区别小结

select * from table where sum(字段)>100

select * from table group by 字段 having 字段>10

SELECT
DISTINCT <select_list>
FROM <left_table>
<join_type> JOIN <right_table>
ON <join_condition><strong>
WHERE</strong> <where_condition>
GROUP BY <group_by_list><strong>
HAVING</strong> <having_condition>
ORDER BY <order_by_condition>
LIMIT <limit_number>

select name as aa from student where aa > 100 (错误)
select name as aa from student group name having  aa > 100 (正确)

select  *  as aa from student where count(*) > 1 (错误)
select *  from student group name having  count(name) > 1 (正确)

SELECT e.employee_name, d.department_name  
FROM employees e  
JOIN departments d ON e.department_id = d.department_id  
WHERE e.salary > 10000 AND d.department_name = 'IT';

SELECT c.customer_name, SUM(o.order_amount) AS total_amount  
FROM customers c  
JOIN orders o ON c.customer_id = o.customer_id  
GROUP BY c.customer_name  
HAVING SUM(o.order_amount) > 1000;