The VALUES clause or building tables out of nothing
The VALUES clause is probably one of the most misused features in SQL. If you look at SQL forums online, you’ll see people use it as the second clause in an insertion statement, but they only use it to...
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Getting Out of Character
Pre-Unicode Younger programmers have grown up with ASCII and Unicode as the only ways of representing character data in a computer. But in the dark ages, before we invented dirt and entered into the...
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The GROUP BY Clause
When you’re learning SQL DML, the most complicated clause is typically the GROUP BY. It’s a fairly simple grouping based on values from the FROM clause in a SELECT statement. It’s what a mathematician...
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T-SQL Fundamentals: Controlling Duplicates
When people start learning a new field, for example T-SQL, it’s tempting to spend very little time trying to understand the fundamentals of the field so that you can quickly get to the advanced parts....
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First Normal Form Gets No Respect
Dr. Codd first described the relational model in a paper in Communications of the ACM (CACM 13 No 6; June 1970). Some more work followed up after that by other people, giving us normal forms and other...
View ArticleThe NTILE Function
The SQL NTILE() is a window function that allows you to break a table into a specified number of approximately equal groups, or <bucket count>. For each row in a grouping, the NTILE() function...
View ArticleWhen an update doesn’t update
Tell me if you’ve heard this one before: I changed data from my application, but when I checked the database, I couldn’t see the change! I’ve seen this. Loads. It can be quite perplexing for folks...
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Using a SQL Tokenizer
Imagine this: you have several directories full of SQL script files, and you need to know where a certain table is used. You’d rather like the context too, so you can check the whole SQL Expression and...
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Eager Aggregation in SQL queries
Aggregation is a widely used way to summarize the content of a database. It is usually expressed with GROUP BY clause or just using aggregate functions (like COUNT or SUM). When the database engine...
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Two-Dimensional Interval Packing Challenge
Packing intervals is a classic SQL task that involves packing groups of intersecting intervals to their respective continuous intervals. In mathematics, an interval is the subset of all values of a...
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