CTE in SQL Server Examples
In this article we cover what a Common Table Expression CTE is and how to write a CTE for doing selects, inserts, deletes, updates and more.
2021-06-02
CTE
Optimize Your SQL by Reformulating the Spec
As SQL developers, we tend to think of performance tuning in terms of crafting the best table indices, avoiding scalar and table valued functions, and analyzing query plans (among other things). But sometimes going back to the spec and applying some properties of elementary math can be the best way to begin to improve performance of SQL queries which implement mathematical formulas. This article is a case study of how I used this technique to optimize my SQL implementation of the Inverse Simpson Index.
2021-05-07 (first published: 2019-09-12)
5,394 reads
Files with larger disk consumption
This script features as we can through the CTE Top10FilesWithLargerDiskConsumption the top ten data files that are showing greater consumption of hard drive related data-reading activities.
2019-01-15 (first published: 2019-01-08)
1,060 reads
2018-07-12
1,152 reads
Implementing John Conway's Game of Life in Microsoft SQL Server
A fun exercise, using CTEs to implement John Conway's Game of Life cellular automata simulation
2018-02-19 (first published: 2015-09-22)
6,623 reads
2015-04-28
1,760 reads
Cursor-Killing: Accessing Data in the Next Row
Cursors are considered by many to be the bane of good T-SQL. What are the best ways to avoid iterative T-SQL and to write queries that look and perform beautifully? This first part in an ongoing series of cursor-killing handles inter-row analysis.
2015-12-18 (first published: 2014-05-27)
22,681 reads
2013-09-25
3,006 reads
2013-09-17 (first published: 2013-09-06)
1,456 reads
Common table expressions and circular references
Finding circular references that are stopping your CTE from working.
2013-09-02 (first published: 2011-01-31)
19,710 reads
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Question of the Day
Fun with JSON I
I have some data in a table:
CREATE TABLE #test_data
(
id INT PRIMARY KEY,
name VARCHAR(100),
birth_date DATE
);
-- Step 2: Insert rows
INSERT INTO #test_data
VALUES
(1, 'Olivia', '2025-01-05'),
(2, 'Emma', '2025-03-02'),
(3, 'Liam', '2025-11-15'),
(4, 'Noah', '2025-12-22');
If I run this query, how many rows are returned?
SELECT *
FROM OPENJSON(
(
SELECT t.* FROM #test_data AS t FOR JSON PATH
)
) t; See possible answers