SQL Server express FAQs and solutions)

An error occurred while establishing a connection with the server.. When you connect to SQL Server 2005, the default setting does not allow remote connection to SQL Server may cause this failure. (Provider: SQL network interface, error: 26-An error occurred while locating the specified server/instance)
First, make sure that SQL Server exprss has been installed on the local computer and the SQL Server (sqlexpress) service has been successfully started. If the problem persists, open "SQL Server peripheral application configurator" and select "service and connected peripheral application configurator ", then configure "remote connection" as "using TCP/IP and named pipes at the same time"

An error occurred while starting the process of the user instance. As a result, the user instance of SQL Server cannot be generated.. The connection is closed.
Modify "user instance = true" in the connection string to "user instance = false.
For more information, see non-administrator user instances.

The file 'x: \ website \ app_data \ database. MDF 'cannot be used as a database ''. Additional. The current command has a serious error. Should discard any possible results.
You need to assign the "read" permission for the Users Group to the subfolders and files of the X and X partitions.

An error occurred while attempting to append the automatically named database to the file X: \ website \ app_data \ database. MDF. A database with the same name already exists, or the specified file cannot be opened or located in the UNC shared directory.
Check that the Users Group's "read" permission has been assigned to the subfolders and files of the X and X partitions. If the problem persists, use SQL Server Management studio to connect to the sqlexpress database instance and check whether the database named "Database" exists. If yes, just remove the database with the same name.. (Especially this one can easily cause inexplicable errors)

The default database cannot be opened.. Logon Failed.
User 'nt Authority \ Network service' Login Failed.
The read and write permissions of database file database. MDF are set to only available for network service. The solution is to stop the SQL Server (sqlexpress) service first, then integrate permissions from the parent item, and then start the SQL Server (sqlexpress) service again.