BCS (Business connectivity Services) in SharePoint2010

Add content type in sharepoint designer

Then click on operations design view in left top.

1.       Click on add connection

2.       Choose SQL server in drop down.

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5) Once created successfully, you should see your new BDC service application

Click on Business Data Connectivity Services, below screen will appear where you can see your external content type created.

Select external content type and set permission as shown.

Give permission edit, execute and select all checkbox as shown below

Click ok finally.

Now browse again external list.

If it again shows error then follow this step.

Go to database server the external list is connected to and check the user loggedin to application now to see external list is added to that database server also.

Click on security in SQL server studio.

Check for if SharePoint logged in user exist in database users.

Add user by clicking on Login->New Login

Enter login name

Select server roles

Select server roles

Click User Mappings and select database name to map.

Click ok

Refresh External List in browser now.