Welcome to the SQL Query Collection repository! This collection is designed to showcase essential SQL concepts through practical examples. The queries cover a wide range of database operations, from basic data selection to advanced performance analysis. Whether you're a beginner or looking to sharpen your SQL skills, you'll find valuable examples here.
- JOINS, GROUP BY, HAVING: Combining and aggregating data across multiple tables.
- Aggregate Functions: Using functions like
SUM,COUNT, and others for in-depth data analysis. - Filtering Data: Using
WHEREclauses for conditional filtering and handling dynamic parameters. - Date Operations: Filtering data based on date ranges and specific time frames.
- Selecting data from tables with conditions such as price, quantity, and location.
- Basic
SELECT,WHERE, and simple aggregate functions.
- Aggregating data for reporting purposes (e.g., total sales, order counts).
- Finding top performers, such as high-value customers or best-selling products.
- Calculating totals by category or customer, often involving complex joins.
- Loyal Customers Report: Identifying customers with 10+ orders, their total spending, and the country they ordered from most frequently.
- Revenue-Generating Employees: Listing employees who have generated over 5,000 TL in sales, with the help of scalar functions.
- Search Products by Name: A stored procedure to search products based on a keyword with optional price filtering.
- Non-clustered indexes are created conditionally to enhance performance during high-read operations (e.g.,
JOINandWHEREfilters onCustomerID,EmployeeID,OrderID,ProductName, andUnitPrice). - Query performance is significantly improved by utilizing proper indexes.
- Demonstrates the use of CREATE PROCEDURE and CREATE FUNCTION with parameters and default values to support reusable, parameterized querying.
- Allows for dynamic queries that are flexible and efficient.