How to Learn SQL: A Step-by-Step Roadmap for Beginners
A clear, 9-stage plan to learn SQL from zero: what to learn first, in what order, how long each stage takes, and a free tutorial for every step.
SQL String Functions Explained Simply (SQL Server and MySQL)
The SQL string functions you’ll use most in SQL Server and MySQL: CONCAT, LEN, TRIM, SUBSTRING, CHARINDEX, REPLACE and STRING_AGG, plus the NULL trap that blanks whole results.
5 Best SQL Server Books for T-SQL Developers
The best Microsoft SQL Server and T-SQL books, from a beginner-friendly tour to Itzik Ben-Gan’s T-SQL Fundamentals and the Administration Inside Out reference.
5 Best SQL Books for Absolute Beginners
Never written a query? These five SQL books are written for complete beginners, from the visual Head First SQL to the hands-on SQL Cookbook.
SQL Server Performance Troubleshooting: A Practical Step-by-Step Guide
A practical, step-by-step process for slow SQL Server queries: describe the symptom, check what’s running and blocking, read the plan, fix indexes and statistics, and measure the result.
Missing Indexes in SQL Server: How to Find Them, and When Not to Add Them
SQL Server suggests missing indexes in the execution plan and the DMVs, but copying them blindly creates duplicates and slows writes. Here’s how to find them, read them, and decide.
SQL Date Functions Explained Simply (SQL Server and MySQL)
The date functions you’ll use most in SQL Server and MySQL: current date, DATEADD, DATEDIFF, month end and formatting, plus the BETWEEN mistake that makes monthly totals wrong.
UNION vs UNION ALL in SQL Explained Simply
UNION removes duplicates, UNION ALL keeps every row and is faster. Learn when to use each, the rules every UNION must follow, and the trap that can make your totals wrong.
HAVING vs WHERE in SQL Explained Simply
WHERE filters rows before grouping. HAVING filters groups after GROUP BY. See the difference with a simple sales example, the logical query order, and common mistakes.
Index Seek vs Index Scan: Why SQL Server Ignores Your Index
You created an index but SQL Server still scans the table. Here are the 8 most common reasons, from functions on columns to implicit conversions, with the fix for each.