📅 30-Day SQL Learning Plan (3–4 Hours Per Day)

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This is perfect for you because you follow daily learning style + practical projects.

🔵 WEEK 1 — SQL Basics (Day 1–7)

Day 1

  • What is SQL?

  • Types of SQL (DDL, DML, DQL, TCL)

  • Install SQL Server / MySQL / PostgreSQL

  • CREATE DATABASE & CREATE TABLE

  • SELECT basics

⏳ 3–4 hrs
📝 Practice 15–20 SELECT queries.

Day 2

  • WHERE clause

  • Comparison operators

  • AND / OR / NOT

  • ORDER BY

  • LIMIT / TOP

📝 Practice filtering 40–50 questions.

Day 3

  • DISTINCT

  • IN / NOT IN

  • BETWEEN

  • LIKE (patterns)

📝 Practice pattern matching queries.

Day 4

  • Functions

    • COUNT, SUM, AVG, MIN, MAX

  • GROUP BY

  • HAVING

📝 20 aggregation questions.

Day 5

  • INSERT

  • UPDATE

  • DELETE

  • Truncate vs Delete vs Drop

Day 6

  • JOINS

    • INNER

    • LEFT

    • RIGHT

    • FULL OUTER

    • CROSS JOIN

📝 20 Join queries.

Day 7

  • All JOIN practice day

  • Mini project: Customers + Orders

⏳ Full revision day.

🔵 WEEK 2 — Intermediate SQL (Day 8–14)

Day 8

  • Subqueries (Single row, Multi row)

Day 9

  • Correlated Subqueries

  • EXISTS / NOT EXISTS

Day 10

  • UNIONS

  • VIEWS

  • Constraints (PK, FK, Unique, Check)

Day 11

  • String functions (LTRIM, RTRIM, SUBSTRING, CHARINDEX)

  • Replace values

  • Upper/Lower

Day 12

  • Date functions (GETDATE, DATEADD, DATEDIFF, FORMAT)

Day 13

  • CASE WHEN (very important)

Day 14

  • Revision + Practice 50 questions

  • Small project: e-commerce dataset analysis

🔵 WEEK 3 — Advanced SQL (Day 15–21)

Day 15

  • CTE (WITH clause)

  • Recursive CTE

Day 16

  • Window Functions

    • ROW_NUMBER

    • RANK

    • DENSE_RANK

Day 17

  • Window Functions part-2

    • LAG

    • LEAD

    • Moving averages

    • PARTITION BY

Day 18

  • PIVOT and UNPIVOT

Day 19

  • Stored Procedures

  • Functions (Scalar, Table-valued)

Day 20

  • Transactions

    • COMMIT

    • ROLLBACK

    • SAVEPOINT

Day 21

  • Temporary tables

  • Table variables

  • Try-Catch in SQL

  • Revision

🔵 WEEK 4 — Expert SQL for Data Engineering (Day 22–30)

Day 22

  • MERGE statement

  • Upsert logic

  • Slowly Changing Dimensions (SCD1)

Day 23

  • SCD2 using SQL

  • Audit columns (CreatedAt, UpdatedAt)

Day 24

  • Control tables for incremental load

  • Watermarking logic

    • MAX(DateColumn)

    • MAX(ModifiedDate)

Day 25

  • Building Incremental Load Query

  • Deduplication SQL (ROW_NUMBER + DELETE DUPs)

Day 26

  • Query Optimization

  • Execution plan reading

  • Indexes

    • Clustered

    • Non-clustered

    • Covering index

    • Index seek vs scan

Day 27

  • Error Handling

  • Dynamic SQL

Day 28

  • Partition tables

  • Large table strategies

  • Performance tuning

Day 29

✨ Final Project (Real Data Engineering Level)
Build SQL for:

  • Full load

  • Incremental load

  • Dedup

  • SCD2 merge

  • Gold KPI queries

Dataset: AdventureWorks (you already have it!)

Day 30

🎉 Final Revision + Prepare Interview Questions

  • 100 SQL interview questions

  • 10 real-time scenarios

  • 5 coding questions

⭐ After 30 Days You Will Become:

✔ Strong in SQL
✔ Able to write production-ready queries
✔ Ready for Data Engineering interviews
✔ Able to design SQL pipelines (Fabric/ADF/Databricks)
✔ Can implement SCD1/SCD2, MERGE, Incremental loads
✔ Expert in window functions & optimization

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