Relational database
Microsoft's enterprise relational database engine.
A full-featured RDBMS with T-SQL, a cost-based optimizer, columnstore indexes, in-memory OLTP, Always On availability groups and deep tooling. Runs on Windows, Linux, containers and as Azure SQL.
SQL ServerBeginnerError 8152 never said which column. Message 2628 on SQL Server 2019+ (or trace flag 460 on 2016/2017) names it. Then fix the data or the column, and watch for silent truncation.
#data-types#troubleshooting#t-sql
SQL ServerIntermediateA diagnostic catalogue of slow query causes in SQL Server: how to tell running from waiting, the plan or wait signature of each cause, and the fix.
#execution-plans#performance#troubleshooting
SQL ServerIntermediateA query-first method: find the expensive queries, read the plan for signs the missing index DMVs never report, build the index online safely, then verify and roll back.
#execution-plans#indexing#performance
SQL ServerIntermediateHow to measure SQL Server query performance with Query Store, DMVs and Extended Events, pick targets by total resource use, and check the settings that affect every query.
#configuration#db-administration#execution-plans
SQL ServerIntermediateQuery sys.dm_db_missing_index_details and its companion DMVs, read the numbers critically, find the queries behind each suggestion and merge them into the few indexes worth creating.
#db-administration#execution-plans#indexing
SQL ServerAdvancedA table-by-table workflow for tuning existing SQL Server indexes: find unused and overlapping indexes, merge them, and replace blanket rebuilds with statistics updates.
#db-administration#indexing#maintenance
SQL ServerBeginnerA 200 GB .ldf for a 20 GB database? Shrinking only treats the symptom. log_reuse_wait_desc tells you the real cause, and here's how to fix each one.
#maintenance#transactions#troubleshooting
SQL ServerIntermediateSame proc, same code, suddenly 100× slower, and fast again when you run it in SSMS. Here's how parameter sniffing causes it, how to prove it and the fixes that actually hold.
#execution-plans#performance#troubleshooting
SQL ServerBeginnerIt's caching by design, not a leak, but the default limit is 'everything'. How to set max server memory and tell real memory pressure from a full buffer pool.
#configuration#internals#performance
SQL ServerIntermediateNOLOCK doesn't just risk dirty reads. It can skip rows, count rows twice and fail with error 601. Read Committed Snapshot Isolation removes the blocking without the wrong answers.
#concurrency#locking#transactions
SQL ServerIntermediateExecution plans tell you exactly how SQL Server ran your query. Learn which operators matter, how to spot bad estimates and what the warnings really mean.
#execution-plans#performance#t-sql
