Dive into the most crucial SQL command with this comprehensive tutorial on the SELECT statement, the powerhouse of data extraction from SQL Server databases. You’ll start by setting up your environment with the free SQL Server Express and SSMS, then move quickly into foundational queries. Learn to create tables (CREATE TABLE) and populate them (INSERT) before mastering the basics of SELECT * to view all data. Crucially, discover why it’s best practice to move beyond the wildcard (*) and instead select specific columns to optimize server performance and limit unnecessary load. This guide ensures you build a strong foundation, making your data retrieval both accurate and efficient.
Advance your SQL skills by learning to filter, sort, and summarize your data effectively. This tutorial provides a deep dive into the WHERE clause to limit rows based on single or multiple conditions (e.g., filtering employees by department and salary). You’ll master the ORDER BY clause to sort results in ascending or descending order across one or more columns, giving structure to your output. Furthermore, unlock the power of aggregate functions like COUNT, SUM, and AVG, and learn to apply them using GROUP BY to get per-department summaries. Finally, understand the difference between WHERE and HAVING, using the latter to filter results based on aggregated values, and utilize the TOP keyword (or LIMIT) to easily extract the highest or lowest records.
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