从两个不使用其中一个的sql视图中进行选择

我有这个sql视图，这不是我的代码：

SELECT
    `view_combined_rev_data`.`date` AS `date`,
    `view_combined_rev_data`.`book_title` AS `book_title`,
    `view_combined_rev_data`.`marketplace` AS `marketplace`,
    `view_combined_rev_data`.`amazon_kdp_avg_list_price` AS `amazon_kdp_avg_list_price`,
    `view_combined_rev_data`.`amazon_kdp_royalty_type` AS `amazon_kdp_royalty_type`,
    `view_combined_rev_data`.`amazon_kdp_revenue_in_usd` AS `amazon_kdp_revenue_in_usd`,
    `view_combined_rev_data`.`amazon_kdp_royalty_in_usd` AS `amazon_kdp_royalty_in_usd`,
    `view_combined_rev_data`.`amazon_kdp_paid_downloads` AS `amazon_kdp_paid_downloads`,
    `view_combined_rev_data`.`amazon_kdp_free_downloads` AS `amazon_kdp_free_downloads`,
    `view_combined_rev_data`.`amazon_ku_pages_read` AS `amazon_ku_pages_read`,
    `view_combined_rev_data`.`amazon_ku_revenue_in_usd` AS `amazon_ku_revenue_in_usd`,
    `view_combined_rev_data`.`create_space_revenue_in_usd` AS `create_space_revenue_in_usd`,
    `view_combined_rev_data`.`create_space_royalty_in_usd` AS `create_space_royalty_in_usd`,
    `view_combined_rev_data`.`create_space_paperbacks_sold` AS `create_space_paperbacks_sold`,
    (
        (
            `view_combined_rev_data`.`amazon_kdp_revenue_in_usd` + `view_combined_rev_data`.`amazon_ku_revenue_in_usd`
        ) + `view_combined_rev_data`.`create_space_revenue_in_usd`
    ) AS `daily_total_revenue`,
    (
        (
            `view_combined_rev_data`.`amazon_kdp_royalty_in_usd` + `view_combined_rev_data`.`create_space_royalty_in_usd`
        ) + `view_combined_rev_data`.`amazon_ku_revenue_in_usd`
    ) AS `daily_total_royalty`
FROM
    `view_combined_rev_marketplace_data` `view_combined_rev_data`

我的问题很简单： 为什么在此行中使用

查看\u组合\u修订\u市场\u数据
。我在其他地方找不到使用它的代码，所以我可以简单地删除它吗

FROM
    `view_combined_rev_marketplace_data` `view_combined_rev_data`

这是您的
FROM
条款：

FROM `view_combined_rev_marketplace_data` `view_combined_rev_data`

第一个名称，
view\u combined\u rev\u marketplace\u data
是数据库中存在的表或视图（可能是视图）的名称

第二个名称是表别名，
view\u combined\u rev\u data
。这就是查询中引用表/视图的方式

我建议您使用表/视图别名，这些别名是表/视图名称的缩写，如下所示：

FROM `view_combined_rev_marketplace_data` vcrmd

然后，对列的引用如下所示：

SELECT vcrmd.`date` AS `date`,
       vcrmd.`book_title` AS `book_title`,
       . . .

这将进一步简化为：

SELECT vcrmd.`date`,
       vcrmd.`book_title`,
       . . .

在这种情况下，列别名（在
后面给出的名称为
）是不必要的，因为它默认为列名。但是请注意，本地编码样式可能建议使用显式列别名

FROM
    `view_combined_rev_marketplace_data` `view_combined_rev_data`

这不是两个视图，而是一个视图
view\u combined\u rev\u marketplace\u data
，别名为
view\u combined\u rev\u data

当使用别名引用表/视图/函数时，必须在语句中使用别名，而不是在对象名称中使用别名。别名通常用于提供对SQL对象的较短或更可读的引用。在本例中，它相对较长。
这是实际的表名。视图\组合\修订\数据是一个表别名。（相当长的一个…）