Missing Data
When we don't have all the information needed to model data, we often use NULL. However, that causes other issues.
2021-04-12
2,807 reads
Joe Celko
Mathematicians and SQL
Georg Ferdinand Ludwig Philipp Cantor is considered the creator of set theory, and his theories are the basis for the naïve set theory you learned in school. But there are lots of other mathematicians you should know, such as Hilbert, Frege, Russell, Zermelo and Dedekind. They made a lot of contributions, too. Hilbert Hilbert is […]
2021-01-19
5,685 reads
Data Element Names and Scoping Rules in SQL
How you name data elements in databases and applications programs has often been a matter of personal taste. Decades ago, when I worked for state government, there is a COBOL programmer who would pick a theme for his programs. The paragraphs and variables would be named based on the current theme. One of his programs […]
2021-01-11
2,213 reads
Stairway to Database Design Level 8: Cursors
This final level to the first landing completes the basics of a SQL database, by explaining what cursors are and why you should never use them.
2020-11-18 (first published: 2011-11-02)
11,828 reads
2020-10-12
2,022 reads
Stairway to Data, Level 4: Temporal Data
Joe Celko tackles the most difficult of all the types of data handled by SQL, temporal data, and explains how to avoid the commonest traps for the unwary programmer
2020-07-08 (first published: 2011-06-15)
11,309 reads
Stairway to Database Design Level 6: Procedure Bodies
Having covered the procedure headers in SQL Server in the previous level, Joe tackles the subject of the contents of stored procedures. In this level, he outlines limitations of TSQL as a procedural language, and what you need to bear in mind when deciding how to use them.
2019-04-03 (first published: 2011-09-21)
13,624 reads
Stairway to Data, Level 1: The Basics
A great deal of the confusion that occurs when a database application is developed comes from a poor understanding of the basics of data. Here, Joe Celko gives a broad coverage of the difficulties you're likely to meet when handling data in databases.
2019-02-06 (first published: 2011-05-12)
20,807 reads
Stairway to Database Design Level 9: Normalization
In the final step of Database Design, Joe Celko gives a simple but effective explanation of the normalization process and why it is important.
2018-02-21 (first published: 2011-11-11)
15,794 reads
Stairway to Database Design Level 7: Triggers
In levels one to four, we built the tables, base and virtual, of a schema. Levels five and six dealt with stored procedures. This level deals with a feature you need to avoid as much as possible; this is article is on Triggers.
2018-01-24 (first published: 2011-09-30)
12,478 reads
Blogs
Automated SQL Server Benchmarking with HammerDB and Docker: A Complete Testing Framework
I’m excited to announce the release of a new open-source project that fully automates...
T-SQL Snapshot Backups on Availability Group Secondary Replicas
One of my favourite features of SQL Server 2022 was the T-SQL Snapshot Backups....
The Book of Redgate: Hours
By Steve Jones
I have said and written this many times: Redgate Software is the type of...
Forums
Optional Parameter Plan Optimization in SQL Server 2025: Fixing the Kitchen-Sink Search Procedure
Comments posted to this topic are about the item Optional Parameter Plan Optimization in...
AI Experience Gap that we keep talking about
Comments posted to this topic are about the item AI Experience Gap that we...
Question of the Day
ORDER BY alias
There is a table tmp_tab:
CREATE TABLE tmp_tab ( id int, val int );
INSERT INTO tmp_tab VALUES (1, 1), (2, NULL), (3, 3), (4, 4), (5, 5);You want to order the rows ids by the following expression:
ISNULL(val, id) + 1Which of the following queries produces the expected ordering and why? (Select all correct) See possible answers