sql查询数量

如题，请各位大神具体分一下。我们公司这边在数据库设计时，为了减少join连表查询，然后把很多字段都放在了同一张表里面，有的数据库表单表字段数超过了50个。

一对多关系的数据,比如订单和订单商品，要一起显示订单和其商品信息，怎么样查询最优就像淘宝一样，每个订单（order表）对应多个商品(order_item表)时，查询订单信息必须把该订单的商品主要信息也显示出来。

该查询为我提供了每个产品ID的结果，但我需要售出的商品总数。我不知道该怎么做。这是我的查询：select count(pro.ProductID),pro.Name,pro.ListPrice from Product as pro join SalesOrderDetail as sod on(pro.ProductID=sod.ProductID)...

MySQL：查询字段数量多少对查询效率的影响

这个问题是最近在分析一个SQL时发起的疑问，然后请教高鹏(重庆八怪)老师，八怪老师予以解答，特此转载老师的文章(本文内容格式略有调整)。源码版本：5.7.22 一、问题由来我们知道执行计划的不同肯定会带来效率的不同，但是在本例中执行...

PageHelper在大数据量下如何提高SQL查询效率？

sql查询，将第一行值的多出数量加入第二行

SQL 查询一个结果，包含数量1，数量2，数量3 三列，sql如何实现：当第一行数量2>数量1时，超过的数量加入第二行的数量2，当第二行的数量2>数量1时，多出数量加入第三行，以此类推

mysql中使用limit查询，如何获得查询的数量

我从数据库中取出前十条数据但是有的表中数据并不够10条，这时该怎么获得数据库里的数据总数这样不行，得到的是所有的数据，limit限制就没有了作用

使用一个T-SQL语句批量查询数据表占用空间及其行数

原文:使用一个T-SQL语句批量查询数据表占用空间及其行数要找到数据库中数据表占用的空间和存在的行数。可以使用sp_spaceused搭配数据表的名称。就可以产生该表耗用的空间和现有行数。如：USE ADVENTUREWORKS GO EXEC sp_spaceused[Sales....

由于分区表中的数据量非常大，怎么用SQL查询准确的统计出分区所占用数据库空间大小？

MySql执行分页时查询统计数据量的Sql语句差别及性能

现在开发系统，涉及到了分页查询，在做的时候就在想，能不能自动把查询sql语句通过参数自动封装成能够统计查询语句不在分页条件下查询出的数据量有多大，例如一般做法是：然后就可以得出分页的相关数据了现在想着的逻辑是：这样两种方式在...

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云数据库SQL Server，具有企业许可授权，权限更为开放，引擎功能更为强大。能完美支持Windows平台的.NET架构，支持复杂SQL查询，性能优秀，并有强大的可视化管理工具，帮助您轻松管理数据。

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