[英]duplicated rows in select query
I am trying to run a query to get all the customers
from my database.我正在尝试运行查询以从我的数据库中获取所有
customers
。 These are my tables in a diagram :这些是我在图表中的表格:
when running the query by joining the table Companies_Customers and the Customers table based on the customerId in both tables(doesn't show in the join table in the pic), I get duplicate rows, which is not the desired outcome.当通过连接表 Companies_Customers 和基于两个表中的 customerId 的客户表运行查询时(未显示在图片的连接表中),我得到重复的行,这不是所需的结果。 This is normal from a database standpoint since a Customer can be related to different companies (Companies can share single customer).
从数据库的角度来看,这是正常的,因为客户可以与不同的公司相关(公司可以共享单个客户)。
My question is how do I get rid of the duplication via SQL.我的问题是如何通过 SQL 消除重复。
There can be 2 approaches to your problem.您的问题可以有 2 种方法。
Either only select data from Customers table:仅从客户表中选择数据:
SELECT * FROM Customers
Or select from both tables joined together, but without CompanyName and with GROUP BY CompanyCustomerId
- although I highly suggest the first approach.或者从连接在一起的两个表中选择,但没有 CompanyName 和
GROUP BY CompanyCustomerId
- 尽管我强烈建议第一种方法。
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