初识 HAVING
关于 SQL 中的 HAVING,相信大家都不陌生,它往往与 GROUP BY 配合使用,为聚合操作指定条件
说到指定条件,我们最先想到的往往是 WHERE 子句,但 WHERE 子句只能指定行的条件,而不能指定组的条件…
因为where关键字无法与合计函数一起使用,例如sum(),avg()等,所以当有条件的话,需要放在having下。 eg:我们希望查找订单总金额少于 2000 的客户。 SELECT Customer,SUM(OrderPrice) FROM Orders
GROUP BY Customer
HAVING SUM(OrderPrice)<…
定义:HAVING 也是条件筛选语句,是放在group by 的后面。
基本语法:
SELECT <字段名>
FROM <表名>
GROUP BY <字段名>
HAVING <筛选条件>;1. HAVING 与 WHERE 的区别
HAVING语句与 WHERE 语句都是条件筛选语句&…
注:本文为 “Feynman diagrams” 相关文章合辑。
机翻,未校。
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