Find consecutive days with gaps and islands, rank the longest streak per user, and define a current streak using the right business date.
Get the Second Row From a Table in SQL Server
To get the second row from a table, first decide what second means, because a table has no order until you give it one. This post builds a small demo and compares ROW_NUMBER, OFFSET and FETCH, and TOP inside TOP. It also covers every second row, the second row in each group, ties and the cost of each method.
Why Query Store Actual Operation Mode is Not Same as Requested? – Interview Question of the Week #248
Question: Why Query Store Actual Operation Mode is Not Same as Requested? Query Regression (poor performing queries, once working great)
Session Wait Stats: Find the Query Behind a Wait Type
Session wait stats tell you which session produced a wait type, and the input buffer tells you which query that session ran. This post shows how to see who waits right now, how to read the wait history of each session, and how to join them to the query text. It also explains the THREADPOOL wait.
SQL SERVER – Upgrade Rule Failure Error: No Custom Security Extensions
Let us learn about upgrade the rule failure error in this blog post and learn how we can fix the error. Locate RSReportServer.config
Parallel Plans: Reading Gather Streams and Repartition Streams
Read Gather Streams and other parallel exchanges, inspect rows per thread and spill evidence, and relate exchange waits to actual work.
Does GROUP BY Sort Results? Only ORDER BY Guarantees It
Does GROUP BY sort the rows it returns? No: only ORDER BY guarantees an order. This post builds a small demo, shows one GROUP BY query returning two different orders, and reads the plans that explain why.