When Page Prefetching Takes a Back Seat – Exploring Trace Flag 652 in SQL Server
Learn how a trace flag affects SQL Server reading from disk and where this might be a useful thing for you to enable.
2025-09-24
2,531 reads
SQL Server internal storage
2025-05-16
636 reads
2025-01-15
1,873 reads
What happens when we drop a column on a SQL Server table? Where's my space?
You have dropped a column and wondering why you haven't recovered any space? Let's take a look.
2024-08-01 (first published: 2024-04-26)
5,096 reads
Identify Tables With Dropped Columns
How easily can we find tables with dropped columns that need cleanup?
2024-06-07
2,660 reads
2024-04-10
472 reads
Understanding CRUD Operations on Tables with B-tree Indexes, Page-splits, and Fragmentation
Introduction Every DML transaction reads the data before it makes any changes. Not only during a SELECT query, but when you run any DML statement, insert, update, or delete, SQL Server first fetches a bunch of pages into the buffer pool locating the desired rows and changes them while synchronously writing to the transaction log […]
2021-05-10
8,971 reads
Understanding CRUD Operations Against Heaps and Forwarding Pointers
In this article, we examine how data changes are made against heaps.
2021-05-03
4,898 reads
Understanding the Internals of a Data Page
In Part 1 of this series, we examine the structure of data pages and how your tables are stored on these pages.
2021-04-13
20,993 reads
2020-06-26
657 reads
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Adding new column with DEFAULT II
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Advanced Deployment Scenarios: Stairway to Reliable Database Deployments Level 7
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You Need a DBA Pipeline
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Question of the Day
Adding new column with DEFAULT II
Which number did the two COUNT(*) return:
DROP TABLE IF EXISTS #tmp CREATE TABLE #tmp (id INT NOT NULL) INSERT INTO #tmp (id) SELECT gs.value FROM GENERATE_SERIES(1, 5) AS gs ALTER TABLE #tmp ADD my_value INT NOT NULL CONSTRAINT df_tmp_my_value DEFAULT 1 SELECT COUNT(*) FROM #tmp AS t WHERE my_value = 1 ALTER TABLE #tmp DROP CONSTRAINT df_tmp_my_value ALTER TABLE #tmp ADD CONSTRAINT df_tmp_my_value DEFAULT 2 FOR my_value SELECT COUNT(*) FROM #tmp AS t WHERE my_value = 1See possible answers