How to Fix SQL Server Does Not Exist or Access Denied Error?

Which Problem Does the Message Mean?

Test the connection outside your application first. Then match the result in this table:

What Should You Collect First?

Four items shorten the search:

1. Copy the exact error text and note whether the failure is constant or intermittent.
2. Find the connection string in the application. Microsoft names Web.config for ASP.NET applications.
3. Open the SQL Server error log of the instance.
4. Check the Windows event logs of the client and the server.

6 Ways to Fix SQL Server Does Not Exist or Access Denied Error

Windows and SQL Server tools handle Methods #1 to #5 and software handles Method #6:

Method #1: Test the Connection With a UDL File (Free)

UDL files test the connection without your application and show which layer fails. Six steps create it:

1. Open File Explorer Options, select the View tab and clear Hide extensions for known file types.
2. Create a text file named sqlconn.txt in C:\temp.
3. Rename the file to sqlconn.udl and select Yes at the extension warning.
4. Double click the UDL file and select Microsoft OLE DB Driver for SQL Server on the Provider tab. Click Next.
5. Type the server in Select or enter a server name, for example tcp:SQLHOST01,1433.
6. Enter the login your application uses and click Test Connection.

Note: A failed test needs a change of protocol. Try tcp:, np: and lpc: one after another. Use the IP address alone and remove the port to test SQL Server Browser.

Passing with lpc: and failing with tcp: means TCP is disabled in Configuration Manager.

Applications with 32 bit providers on 64 bit Windows need the 32 bit dialog. Open %windir%\SysWoW64\cmd.exe and type START C:\TEMP\SQLCONN.UDL.

Method #2: Fix the Connection String (Free)

Passed UDL tests and failing applications point to the string. Five steps compare them:

1. Open the UDL file in Notepad to see the saved string.
2. Open the configuration file of your application.
3. Compare the server name, the instance name and the port in both strings.
4. Replace the application value with the working one.
5. Restart the application.

Note: Name patterns for default instances, named instances and custom ports sit in Could Not Open a Connection to SQL Server Error 40.

Method #3: Check the Services and Protocols (Free)

Check the instance before the client. Four checks follow:

1. Search the error log for the ready message:

Get-ChildItem -Path "c:\program files\microsoft sql server\mssql*" -Recurse -Include Errorlog | Select-String "SQL Server is now ready for client connections."

2. Search the same logs for the listening port:

Get-ChildItem -Path "c:\program files\microsoft sql server\mssql*" -Recurse -Include Errorlog | Select-String "Server is listening on"

3. Test the name and the IP address with ping -a <server name> and ping -a <IP address>.
4. Start SQL Server Browser for a named instance in Configuration Manager.

Note: No ready message means the instance is stopped. How to Fix SQL Server Instance Not Starting explains the fixes.

Method #4: Fix the Login and Database Permissions (Free)

Access denied points to the login. Microsoft requires CONNECT SQL on the server and CONNECT on the database. Four steps check and fix both:

1. Connect to the instance with an administrator login in SSMS.
2. Check the login:

SELECT pr.name, pr.is_disabled, pr.default_database_name,
       pe.permission_name, pe.state_desc
FROM sys.server_principals AS pr
LEFT OUTER JOIN sys.server_permissions AS pe
  ON pr.principal_id = pe.grantee_principal_id
WHERE pr.name = 'CONTOSO\JaneK';

3. Grant the server permission and correct the default database:

GRANT CONNECT SQL TO [CONTOSO\JaneK];
ALTER LOGIN [CONTOSO\JaneK] WITH DEFAULT_DATABASE = [mydb];

4. Grant the database permission to the mapped user:

USE mydb;
GRANT CONNECT TO [JaneK];

Note: Replace the sample names with your own. sp_helplogins 'CONTOSO\JaneK' shows the mapping between the login and the database user.

Method #5: Update the Client Driver (Free)

Compare the failing client with a working one. Four steps narrow the cause:

1. Connect with the same login from another PC.
2. Check the Windows event logs of the failing PC.
3. Update the network driver when the check shows an old version.
4. Select Microsoft OLE DB Driver for SQL Server in the application.

Note: Microsoft calls that driver the latest one with TLS 1.2 and 1.3 support. Legacy SQLOLEDB ships with Windows and fails when the instance requires newer TLS channel bindings. Remove wrong aliases with the steps in Method #5 of the error 40 guide.

Method #6: Export Your Tables Without a Login Using EmailDoctor (Trial Limit Applies)

Permission fixes need an administrator login and you do not always have one. EmailDoctor SQL Database Recovery processes the MDF file copy on your PC and needs no SQL login. Recovered objects include tables, views, functions and stored procedures.

Trial exports cap every table at 25 records and the other objects at 5.

Scan the Copied File

Stop the SQL Server service before you copy the file because Windows refuses to copy an open database file. Six steps scan the copy:

1. Copy the MDF file into a folder on your PC.
2. Start the recovery software and wait for the home screen.
3. Click Open and select the copied file.
4. Choose the scan mode. Quick Scan fits a healthy file.
5. Keep Auto detect or select the SQL Server version.
6. Wait for the scan report.

Export the Tables

Three steps export the data:

7. Select a table to preview the recovered records.
8. Click Export.
9. Select CSV as the export type and a destination folder.

Which Problems Remain After the Fixes?

Five patterns explain the failures that remain:

Frequently Asked Questions

Author’s Verdict

Test the connection with a UDL file before any change. UDL results show whether the name, the login or the application string fails.

Fix the permission with the lowest right that works and keep the connection string in one place.

Use recovery software when the data is due and access remains denied.