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
2,767 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
5,622 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
2,170 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)
11,759 reads
2020-10-12
1,993 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)
11,227 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)
13,529 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.
2019-03-26 (first published: 2011-05-12)
20,677 reads
Stairway to Data, Level 2: Numerics
A confusion about the nature of numbers can lead to a number of problems in database applications. Joe Celko gives a simple guide to the subject
2019-03-26 (first published: 2011-05-18)
12,369 reads
Stairway to Data, Level 3: Strings
Character-handling in SQL is not particularly straightforward, and confusion about collation and character encoding is a common cause of problems with searching, joining, and sorting.
2019-03-26 (first published: 2011-06-01)
9,510 reads
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Question of the Day
Azure SQL Database MAXDOP
When Azure SQL Database was originally released, the MAXDOP was set to 0 for each new database. In Oct 2025, what is the default value for Azure SQL databases?
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