JavaScript Lesson 6: Objects and JSON
Group related data in objects, access nested properties, destructure values, convert to and from JSON with JSON.stringify and JSON.parse — the format every API…
Read article →Coding
Start-to-finish programming for people who work with data: Python, SQL, Java, R, JavaScript, Rust and PowerShell.
JavaScript Lesson 4: Functions and Arrow Functions
JavaScript Lesson 4: Functions and Arrow Functions
Write reusable functions with parameters, default values and return, the shorter arrow function syntax, and where functions are used as values.
Read article →JavaScript Lesson 3: Conditions and Loops
JavaScript Lesson 3: Conditions and Loops
Make decisions with if/else and the ternary operator, compare with ===, and repeat work with for, for...of over arrays and objects, and while.
Read article →JavaScript Lesson 2: Variables, Types and Strings
JavaScript Lesson 2: Variables, Types and Strings
Declare variables with const and let, understand numbers, strings and booleans, use template literals, format Indian numbers with toLocaleString, and common string methods.
Read article →JavaScript Lesson 1: Running JavaScript — Browser Console and Node
JavaScript Lesson 1: Running JavaScript — Browser Console and Node
Run your first JavaScript in the browser console and with Node.js, use VS Code, understand where JavaScript runs, and print output with console.log.
Read article →SQL Intermediate Lesson 10: Project – Customer RFM and Outstanding Payments
SQL Intermediate Lesson 10: Project – Customer RFM and Outstanding Payments
Final project: recency, frequency and monetary scores with NTILE, customer segments, outstanding receivables per customer and average collection days by payment mode.
Read article →SQL Intermediate Lesson 9: Indexes and Query Plans
SQL Intermediate Lesson 9: Indexes and Query Plans
Read EXPLAIN QUERY PLAN, see SCAN turn into SEARCH with an index, build covering indexes, and learn why functions on columns stop indexes working.
Read article →SQL Intermediate Lesson 8: Pivot Reports With CASE
SQL Intermediate Lesson 8: Pivot Reports With CASE
Turn rows into columns with conditional aggregation: sales by status per region, orders per quarter, payment-mode mix and actual vs target with % achieved.
Read article →SQL Intermediate Lesson 7: Recursive CTEs – Org Charts and Date Series
SQL Intermediate Lesson 7: Recursive CTEs – Org Charts and Date Series
Walk a manager hierarchy, build reporting paths, total a team's salary cost and generate a calendar to find days with no orders, using WITH…
Read article →SQL Intermediate Lesson 6: UNION, INTERSECT and EXCEPT
SQL Intermediate Lesson 6: UNION, INTERSECT and EXCEPT
Combine and compare result sets: one list from two tables, customers who bought both products, customers who never bought one, and activity timelines with…
Read article →SQL Intermediate Lesson 5: Joins in Depth – Anti-Joins, Self-Joins, Cross Joins
SQL Intermediate Lesson 5: Joins in Depth – Anti-Joins, Self-Joins, Cross Joins
Find unpaid orders with LEFT JOIN ... IS NULL and NOT EXISTS, list employees with their managers via a self-join, and fill zero months…
Read article →SQL Intermediate Lesson 4: LAG and LEAD – Month-on-Month Growth
SQL Intermediate Lesson 4: LAG and LEAD – Month-on-Month Growth
Compare each row with the previous or next one: month-on-month growth %, days between a customer's orders and the next order date with LAG…
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