The Scariest Lines of Code I’ve Ever Written
06 Nov 2025 #sql
I don’t remember if it was rainy or sunny outside. It was more than five years ago. I was still becoming a senior coder.
I’ve written hundreds of thousands of lines of code. But I still remember this one. As part of my routine, I wrote this query in a stored procedure,
SELECT * FROM dbo.HugeTableWithoutIndexes
WHERE DATEDIFF(DAY, ADateColumn, @InputDate) = 0
I was working with an email system built with Amazon SES. I needed to show all email activity: delivered, opened, bounced, and so on. I wrapped a column in a function. A deadly sin!
The table had millions of records and no indexes. My quer…
The Scariest Lines of Code I’ve Ever Written
06 Nov 2025 #sql
I don’t remember if it was rainy or sunny outside. It was more than five years ago. I was still becoming a senior coder.
I’ve written hundreds of thousands of lines of code. But I still remember this one. As part of my routine, I wrote this query in a stored procedure,
SELECT * FROM dbo.HugeTableWithoutIndexes
WHERE DATEDIFF(DAY, ADateColumn, @InputDate) = 0
I was working with an email system built with Amazon SES. I needed to show all email activity: delivered, opened, bounced, and so on. I wrapped a column in a function. A deadly sin!
The table had millions of records and no indexes. My query forced a full scan of the table. The next thing I knew the server was on fire. Not literally, of course.
Those days I refused to learn SQL, convinced ORMs and NoSQL were enough. I couldn’t have been more wrong. Relational databases and SQL still reign.
Eventually I learned about indexing, scans vs seeks, and SQL Server internals. Shout out to Brent Ozar’s courses.
A painful lesson I will never forget. That’s why learning SQL found its way into my new book, Street-Smart Coding. It isn’t a textbook. It’s a roadmap with 30 proven lessons to help you code like a pro. It’s the guide I wish I had starting out.
Want to avoid painful mistakes like mine? Grab your copy of Street-Smart Coding here