SQL Mindmap 👆

9 tips to learn SQL effectively:

Start with basic queries: SELECT, WHERE, ORDER BY

Understand different JOIN types clearly

Practice with real datasets (like IMDb, HR, Sales)

Learn GROUP BY and aggregate functions (SUM, AVG, COUNT)

Use subqueries and CTEs for complex logic

Explore window functions (ROW_NUMBER, RANK, etc.)

Understand NULLs and how to handle them

Practice writing clean, readable queries

Build mini projects or dashboards using SQL data

#sql

Here are some essential SQL tips for beginners 👇👇

◆ Primary Key = Unique Key + Not Null constraint
◆ To perform case insensitive search use UPPER() function ex. UPPER(customer_name) LIKE ‘A%A’
◆ LIKE operator is for string data type
◆ COUNT(*), COUNT(1), COUNT(0) all are same
◆ All aggregate functions ignore the NULL values
◆ Aggregate functions MIN, MAX, SUM, AVG, COUNT are for int data type whereas STRING_AGG is for string data type
◆ For row level filtration use WHERE and aggregate level filtration use HAVING
◆ UNION ALL will include duplicates where as UNION excludes duplicates 
◆ If the results will not have any duplicates, use UNION ALL instead of UNION
◆ We have to alias the subquery if we are using the columns in the outer select query
◆ Subqueries can be used as output with NOT IN condition.
◆ CTEs look better than subqueries. Performance wise both are same.
◆ When joining two tables , if one table has only one value then we can use 1=1 as a condition to join the tables. This will be considered as CROSS JOIN.
◆ Window functions work at ROW level.
◆ The difference between RANK() and DENSE_RANK() is that RANK() skips the rank if the values are the same.
◆ EXISTS works on true/false conditions. If the query returns at least one value, the condition is TRUE. All the records corresponding to the conditions are returned.

Here you can find essential SQL Resources👇
https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

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Relatable? 😂

𝗧𝗵𝗲 𝗯𝗲𝘀𝘁 𝗦𝗤𝗟 𝗹𝗲𝘀𝘀𝗼𝗻 𝘆𝗼𝘂’𝗹𝗹 𝗿𝗲𝗰𝗲𝗶𝘃𝗲 𝘁𝗼𝗱𝗮𝘆:

Master the core SQL statements—they are the building blocks of every powerful query you'll write.

-> SELECT retrieves data efficiently and accurately. Remember, clarity starts with understanding the result set you need.

-> WHERE filters data to show only the insights that matter. Precision is key.

-> CREATE, INSERT, UPDATE, DELETE allow you to mold your database like an artist—design it, fill it, improve it, or even clean it up.

In a world where everyone wants to take, give knowledge back.

Become an alchemist of your life. Learn, share, and build solutions.

Always follow best practices in SQL to avoid mistakes like missing WHERE in an UPDATE or DELETE. These oversights can cause chaos!

Without WHERE, you risk updating or deleting entire datasets unintentionally. That's a costly mistake.

But with proper syntax and habits, your databases will be secure, efficient, and insightful.

SQL is not just a skill—it's a mindset of precision, logic, and innovation.

Here you can find essential SQL Interview Resources👇
https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

Like this post if you need more 👍❤️

Hope it helps :)

#sql

9 tips to learn SQL for Data Analysis:

🧱 Start with basic queries: SELECT, WHERE, ORDER BY
🔗 Understand different types of JOINs
📊 Use GROUP BY with aggregate functions like SUM, AVG, COUNT
🧮 Practice filtering using HAVING and complex WHERE conditions
🧠 Learn CASE WHEN for conditional logic
🧾 Explore subqueries and Common Table Expressions (CTEs)
🪄 Use WINDOW functions like ROW_NUMBER, RANK, LEAD, LAG
🔍 Understand how to handle NULL values properly
📁 Work on real-world datasets to sharpen your skills

Here you can find essential SQL Interview Resources👇
https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

Like this post if you need more 👍❤️

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#sql

SQL Basics Cheatsheet 👆

SQL Tips

SQL, or Structured Query Language, is a domain-specific language used to manage and manipulate relational databases. Here's a brief A-Z overview by @sqlanalyst

A - Aggregate Functions: Functions like COUNT, SUM, AVG, MIN, and MAX used to perform operations on data in a database.

B - BETWEEN: A SQL operator used to filter results within a specific range.

C - CREATE TABLE: SQL statement for creating a new table in a database.

D - DELETE: SQL statement used to delete records from a table.

E - EXISTS: SQL operator used in a subquery to test if a specified condition exists.

F - FOREIGN KEY: A field in a database table that is a primary key in another table, establishing a link between the two tables.

G - GROUP BY: SQL clause used to group rows that have the same values in specified columns.

H - HAVING: SQL clause used in combination with GROUP BY to filter the results.

I - INNER JOIN: SQL clause used to combine rows from two or more tables based on a related column between them.

J - JOIN: Combines rows from two or more tables based on a related column.

K - KEY: A field or set of fields in a database table that uniquely identifies each record.

L - LIKE: SQL operator used in a WHERE clause to search for a specified pattern in a column.

M - MODIFY: SQL command used to modify an existing database table.

N - NULL: Represents missing or undefined data in a database.

O - ORDER BY: SQL clause used to sort the result set in ascending or descending order.

P - PRIMARY KEY: A field in a table that uniquely identifies each record in that table.

Q - QUERY: A request for data from a database using SQL.

R - ROLLBACK: SQL command used to undo transactions that have not been saved to the database.

S - SELECT: SQL statement used to query the database and retrieve data.

T - TRUNCATE: SQL command used to delete all records from a table without logging individual row deletions.

U - UPDATE: SQL statement used to modify the existing records in a table.

V - VIEW: A virtual table based on the result of a SELECT query.

W - WHERE: SQL clause used to filter the results of a query based on a specified condition.

X - (E)XISTS: Used in conjunction with SELECT to test the existence of rows returned by a subquery.

Z - ZERO: Represents the absence of a value in numeric fields or the initial state of boolean fields.

Getting started with SQL comparison operators.

If you're new to SQL, understanding comparison operators is one of the first things you'll need to learn.

They’re really important for filtering and analyzing your data. Let’s break them down with some simple examples.

Comparison operators let you compare values in SQL queries. Here are the basics:
1. = (Equal To): Checks if two values are the same.
Example: SELECT * FROM Employees WHERE Age = 30; (This will find all employees who are exactly 30 years old).

2. <> or != (Not Equal To): Checks if two values are different.
Example: SELECT * FROM Employees WHERE Age <> 30; (This will find all employees who are not 30 years old).

3. > (Greater Than): Checks if a value is larger.
Example: SELECT * FROM Employees WHERE Salary > 50000; (This will list all employees earning more than 50,000).

4. < (Less Than): Checks if a value is smaller.
Example: SELECT * FROM Employees WHERE Salary < 50000; (This will show all employees earning less than 50,000).

5. >= (Greater Than or Equal To): Checks if a value is larger or equal.
Example: SELECT * FROM Employees WHERE Age >= 25; (This will find all employees who are 25 years old or older).

6. <= (Less Than or Equal To): Checks if a value is smaller or equal.
Example: SELECT * FROM Employees WHERE Age <= 30; (This will find all employees who are 30 years old or younger).

These simple operators can help you get more accurate results in your SQL queries.

Keep practicing and you’ll be great at SQL in no time.

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SQL query optimization techniques

✅ Index Optimization

➡️ Ensure indexes are created on columns that are frequently used in 'WHERE' clauses, 'JOIN' conditions and as part of 'ORDER BY' clauses.
➡️Use composite indexes for columns that are frequently queried together.
➡️Regularly analyze and rebuild fragmented indexes.

✅ Query Refactoring

➡️ Break complex queries into simpler subqueries or use common table expressions (CTEs).
➡️ Avoid unnecessary columns in the 'SELECT' clause to reduce the data processed.

✅ Join Optimization

➡️ Use the appropriate type of join (INNER JOIN, LEFT JOIN, etc.) based on the requirements.
➡️ Ensure join columns are indexed to speed up the join operation.
➡️ Consider the join order, starting with the smallest table.

✅ Use of Proper Data Types

➡️ Choose the most efficient data type for your columns to reduce storage and improve performance.
➡️ Avoid using 'SELECT *', specify only the columns you need.

✅ Query Execution Plan Analysis

➡️ Use tools like 'EXPLAIN or 'EXPLAIN PLAN' to analyze how the database executes a query.
➡️ Look for full table scans, inefficient joins, or unnecessary sorting operations.

✅ Temporary Tables and Materialized Views

➡️ Use temporary tables to store intermediate results that are reused multiple times in complex queries.
➡️ Use materialized views to store precomputed results of expensive queries.

✅ Efficient Use of Subqueries and CTEs

➡️ Replace correlated subqueries with joins when possible to avoid repeated execution.
➡️ Use CTEs to improve readability and reusability, and sometimes performance, of complex queries.

✅ Optimization of Aggregate Functions

➡️ Use indexed columns in 'GROUP BY' clauses to speed up aggregation.
➡️ Consider using window functions for complex aggregations instead of traditional 'GROUP BY'.

✅ Avoiding Functions in Predicates

➡️ Avoid using functions on columns in the 'WHERE' clause as it can prevent the use of indexes.
➡️ Rewrite conditions to allow the use of indexes.

✅ Parameter Sniffing and Query Caching

➡️ Be aware of parameter sniffing issues where SQL Server caches execution plans based on initial parameter values.
➡️ Use query hints or option recompile to address specific performance issues.
➡️ Take advantage of query caching mechanisms where appropriate to reuse execution plans.

🛠 By applying these advanced techniques, you can significantly enhance the performance of your SQL queries and ensure that your database runs efficiently.

SQL Free Resources

Hope it helps :)

You don’t need 6 months to learn it. 90% of real-world SQL can be explained in ONE post.

Let me prove it, read on!

1️⃣ SELECT → Grab Data

SELECT * FROM users;

➡️ Gets everything

SELECT name, age FROM users;

➡️ Gets only what you need

2️⃣ WHERE → Filter Rows

SELECT * FROM users WHERE age > 25;

Use to keep only rows that match a rule ✅

Common filters:
>, <, =, !=, LIKE '%text%'

3️⃣ JOIN → Combine Tables

Real-world data lives in different tables. You need to connect them.

Example:
Get each customer's name and what they bought.

SELECT t1.name, t2.price
FROM t1
JOIN t2 ON t1.id = t2.customer_id;

➡️ This finds matching rows in both tables based on id.

Other JOIN types:

LEFT JOIN = all from t1, plus matches from t2

RIGHT JOIN = all from t2, plus matches from t1

4️⃣ UNION → Stack Tables

Got 2 tables with same columns?

SELECT name, age FROM employees
UNION
SELECT name, age FROM retirees;

➡️ Combines them vertically
Great for merging data sources!

5️⃣ GROUP BY → Summarize

SELECT user_id, COUNT(*) AS order_count
FROM orders
GROUP BY user_id;

➡️ One result per group
Perfect for counts, sums, averages

6️⃣ HAVING → Filter After GROUP BY

SELECT user_id, COUNT(*)
FROM orders
GROUP BY user_id
HAVING COUNT(*) > 5;

➡️ Filters groups
WHERE doesn’t work here — use HAVING

7️⃣ ORDER BY → Sort Data

SELECT * FROM orders
ORDER BY amount DESC;

➡️ Sort from highest to lowest
Use LIMIT to get top 5, 10, etc.

📌 You Just Learned 90% of Real-World SQL

Don’t overthink it.
These 7 commands get you through 90% of the job.

If this was helpful and you want to be a data analyst

→ Join the community of aspiring data analysts: https://whatsapp.com/channel/0029VaGgzAk72WTmQFERKh02

𝗧𝗵𝗲 𝗯𝗲𝘀𝘁 𝗦𝗤𝗟 𝗹𝗲𝘀𝘀𝗼𝗻 𝘆𝗼𝘂’𝗹𝗹 𝗿𝗲𝗰𝗲𝗶𝘃𝗲 𝘁𝗼𝗱𝗮𝘆:

Master the core SQL statements—they are the building blocks of every powerful query you'll write.

-> SELECT retrieves data efficiently and accurately. Remember, clarity starts with understanding the result set you need.

-> WHERE filters data to show only the insights that matter. Precision is key.

-> CREATE, INSERT, UPDATE, DELETE allow you to mold your database like an artist—design it, fill it, improve it, or even clean it up.

In a world where everyone wants to take, give knowledge back. 

Become an alchemist of your life. Learn, share, and build solutions.

Always follow best practices in SQL to avoid mistakes like missing WHERE in an UPDATE or DELETE. These oversights can cause chaos!

Without WHERE, you risk updating or deleting entire datasets unintentionally. That's a costly mistake.

But with proper syntax and habits, your databases will be secure, efficient, and insightful.

SQL is not just a skill—it's a mindset of precision, logic, and innovation.

Here you can find essential SQL Interview Resources👇
https://t.iss.one/mysqldata

Like this post if you need more 👍❤️

Hope it helps :)

#sql