如何查询多个表 [英] How to query with multiple tables

问题描述

我的项目包含2个表格。

DetailsTB和ImageTB



现在DetailsTB包含主键作为两列收据的复合键，Passenger_Name

例如PRIMARY KEY（收据，Passenger_Name）



和这个FOREIGN KEY（收据，Passenger_Name）是ImageTB的主键



例如FOREIGN KEY（Receipt，Passenger_Name）REFERENCES DetailsTB（Receipt，Passenger_Name），PRIMARY KEY（Receipt，Passenger_Name）表ImageTB



我想在两个表中选择记录但是我的查询无法正常工作



我的查询：



cmd =新的SqlCommand（SELECT Picture FROM ImageTB WHERE DetailsTB.Passenger_Name ='+ datagridview_details.Rows [e.RowIndex] .Cells [6] .Value.ToString（）+'AND DetailsTB.Passenger_Name = ImageTB.Passenger_Name，con）;



它给了我各种sqlexception错误。



所以plz帮我查询同样的问题。



提前感谢

My Project contain 2 tables.
DetailsTB and ImageTB

Now DetailsTB contain Primary key as a Composite Key of two column of Receipt,Passenger_Name
e.g. PRIMARY KEY(Receipt, Passenger_Name)

and this FOREIGN KEY(Receipt, Passenger_Name) is Primary key for ImageTB

e.g. FOREIGN KEY (Receipt, Passenger_Name) REFERENCES DetailsTB(Receipt, Passenger_Name), PRIMARY KEY (Receipt, Passenger_Name) for table ImageTB

I want to select record in both table but my query cant work properly

My query:

cmd = new SqlCommand("SELECT Picture FROM ImageTB WHERE DetailsTB.Passenger_Name = '" + datagridview_details.Rows[e.RowIndex].Cells[6].Value.ToString() + "' AND DetailsTB.Passenger_Name = ImageTB.Passenger_Name", con);

it gives me various sqlexception error.

So plz help me for the same query.

thanks in advance

推荐答案

在查询中使用JOIN

use JOIN in your query

cmd = new SqlCommand(string.Format("SELECT Picture FROM ImageTB itb join DetailsTB dtb on dtb.Passenger_Name = itb.Passenger_Name WHERE dtb.Passenger_Name = '{0}'", datagridview_details.Rows[e.RowIndex].Cells[6].Value.ToString()), connection);

你还需要检查atagridview_details.Rows [e.RowIndex] .Cells [6] .Value不为空

（或者你会得到NullReferenceException）



并且还要注意Sql注入

also you need check that atagridview_details.Rows[e.RowIndex].Cells[6].Value is not null
(or you will get NullReferenceException)

and also be aware of Sql injection

我建​​议你看一下JOIN的使用。



基本例子： http://www.w3schools.com/sql/sql_join.asp [ ^ ]

I suggest you look at the use of JOINs.

Basic example: http://www.w3schools.com/sql/sql_join.asp[^]

你必须了解SQL Join才能使用多个表条件。



访问此处了解...



SQL检索数据a来自多个表格 [ ^ ]



或



使用多个表格加入 [ ^ ]

you have to understand about SQL Join to use multiple tables condition.

visit here to understand ...

SQL Retrieve data from multiple tables[^]

or

Use Join With Multiple Tables[^]

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