T-SQL Tuesday #149 – T-SQL Advice you’d give to your younger self

It’s the second Tuesday of the month, so it’s time for the T-SQL Tuesday blog party! This month’s topic is chosen by Camila Henrique (blog): what T-SQL advice would you give to your younger self? Here’s a little list I’d tell anyone starting out with T-SQL:

• you can configure most tools that when you hit Tab, it enters 4 spaces instead
• get the difference between set-based processing and RBAR (aka cursors)
• learn the different types of JOINs
• don’t try to write one giant SQL statement that does it all. Either use common table expressions to clarify your code, or split up and use (temp) tables to store intermediate results.
• learn how indexes work. They’re one of the most fundamental things to learn when it comes to performance tuning.
• learn about SARGable queries, so your indexes are actually used
• learn about window functions, because they’re awesome. I can absolutely recommend the book by Itzik Ben-Gan.
• put everything in source control
• comment your code
• don’t spend too much time on hierarchyid, XML and other exotic stuff, nobody uses it (but you need to learn it for the certification exams)
• learn about dynamic SQL and how you can generate stuff based on metadata
• learn the logical query processing order. E.g. SELECT comes last, FROM comes first.
• get the subtle difference between DISTINCT and GROUP BY to remove duplicates. And don’t forget UNION and UNION ALL are not the same.