SQL Server connection errors have a different message for each cause. The tests here trigger seven of them against a local SQL Server 2025 instance, show what the client says, what the ERRORLOG records, and how to find the port an instance listens on.
SQL SERVER – SQL Server Statistics Name and Index Creation
Guest author Sandip hit Msg 1913 while creating an index, because an index or statistics with that name already existed. A lesson on statistics name and index creation.
SET LOCK_TIMEOUT and Error 1222: Waiting Less for Locks
Set LOCK_TIMEOUT to bound lock waits, reproduce error 1222, clean up the transaction, and retry safely without confusing client timeouts.
SQL SERVER – FIX ERROR – Cannot connect to . Login failed. The login is from an untrusted domain and cannot be used with Windows authentication. (Microsoft SQL Server, Error: 18452)
Error 18452 said my login was from an untrusted domain while I connected from my own machine to 127.0.0.1. Here is the small change that caused it.
SQL SERVER – DQS Error – Cannot connect to server – A .NET Framework error occurred during execution
Opening the DQS client, I hit a long .NET Framework error from SetDataQualitySessions and could not connect. Here is that DQS Error and how I worked through it.
SQL SERVER – Error: Fix – Msg 208 – Invalid object name ‘dbo.backupset’ – Invalid object name ‘dbo.backupfile’
Msg 208, Invalid object name ‘dbo.backupset’, but only in SSMS? A reader’s backup history query failed there while it worked in the app. Here is what was going on.
CHECK Constraints and NULL: Why Unknown Passes the Test
Why does a CHECK (Quantity > 0) happily store a row with no quantity? Three-valued logic, a small demo, and the NOT NULL fix.