UPDATE customers SET email = 'new@email.com' WHERE customer_id = 123;

--This updates the email address for the customer with ID 123.

Joins allow you to combine data from multiple tables based on related columns

SQL Notes Part-1

Like if you need more content on SQL 😄❤️

SQL Notes Part-2
Window Functions

SQL Notes Part-3
(Cascading actions and Normalisation concepts)

SQL Notes PART-4
Data Wrangling functions on string data types 😄👍

Leveling up with SQL
👇👇
https://news.1rj.ru/str/learndataanalysis/459

SQL Quick Guide
For more join -> t.me/sqlspecialist

Free resources to learn SQL

Udacity free course- https://imp.i115008.net/AoAg7K

For Practice- https://stratascratch.com/?via=free

SQL Quick Notes to refresh your concepts

Introduction to Databases with SQL: Free Harvard Course
👇👇
https://cs50.harvard.edu/sql/2023/

If you are trying to transition into the data analytics domain and getting started with SQL, focus on the most useful concept that will help you solve the majority of the problems, and then try to learn the rest of the topics:

👉🏻 Basic Aggregation function:
1️⃣ AVG
2️⃣ COUNT
3️⃣ SUM
4️⃣ MIN
5️⃣ MAX

👉🏻 JOINS
1️⃣ Left
2️⃣ Inner
3️⃣ Self (Important, Practice questions on self join)

👉🏻 Windows Function (Important)
1️⃣ Learn how partitioning works
2️⃣ Learn the different use cases where Ranking/Numbering Functions are used? ( ROW_NUMBER,RANK, DENSE_RANK, NTILE)
3️⃣ Use Cases of LEAD & LAG functions
4️⃣ Use cases of Aggregate window functions

👉🏻 GROUP BY
👉🏻 WHERE vs HAVING
👉🏻 CASE STATEMENT
👉🏻 UNION vs Union ALL
👉🏻 LOGICAL OPERATORS

Other Commonly used functions:
👉🏻 IFNULL
👉🏻 COALESCE
👉🏻 ROUND
👉🏻 Working with Date Functions
1️⃣ EXTRACTING YEAR/MONTH/WEEK/DAY
2️⃣ Calculating date differences

👉🏻CTE
👉🏻Views & Triggers (optional)

Here is an amazing resources to learn & practice SQL: https://bit.ly/3FxxKPz

Share with credits: https://news.1rj.ru/str/sqlspecialist

Hope it helps :)

Free Data sets for Data Science & Machine Learning Projects
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https://news.1rj.ru/str/DataPortfolio

SQL Topicwise Interview Questions & Answers

https://www.linkedin.com/posts/sql-analysts_sql-intrrview-preparation-activity-7129458058409181184-UJKb

Top 5 SQL Functions

https://news.1rj.ru/str/sqlanalyst

1. SELECT Statement:
- Function: Retrieving data from one or more tables.
- Example: SELECT column1, column2 FROM table WHERE condition;

2. COUNT Function:
- Function: Counts the number of rows that meet a specified condition.
- Example: SELECT COUNT(column) FROM table WHERE condition;

3. SUM Function:
- Function: Calculates the sum of values in a numeric column.
- Example: SELECT SUM(column) FROM table WHERE condition;

4. AVG Function:
- Function: Computes the average value of a numeric column.
- Example: SELECT AVG(column) FROM table WHERE condition;

5. GROUP BY Clause:
- Function: Groups rows that have the same values in specified columns into summary rows.
- Example: SELECT column, AVG(numeric_column) FROM table GROUP BY column;

These functions are fundamental in SQL and are frequently used for various data manipulation tasks, including data retrieval, aggregation, and analysis.

*SQL Interview Questions which can be asked in a Data Analyst Interview.*

1️⃣ What is difference between Primary key and Unique key?

◼Primary key- A column or set of columns which uniquely identifies each record in a table. It can't contain null values and only one primary key
can exist in a table.

◼Unique key-Similar to primary key it also uniquely identifies each record in a table and can contain null values.Multiple Unique key can exist in a table.

2️⃣ What is a Candidate key?

◼A key or set of keys that uniquely identifies each record in a table.It is a combination of Primary and Alternate key.

3️⃣ What is a Constraint?

◼Specific rule or limit that we define in our table. E.g - NOT NULL,AUTO INCREMENT

4️⃣ Can you differentiate between TRUNCATE and DELETE?

◼TRUNCATE is a DDL command. It deletes the entire data from a table but preserves the structure of table.It doesn't deletes the data row by row hence faster than DELETE command, while DELETE is a DML command and it deletes the entire data based on specified condition else deletes the entire data,also it deletes the data row by row hence slower than TRUNCATE command.

5️⃣ What is difference between 'View' and 'Stored Procedure'?

◼A View is a virtual table that gets data from the base table .It is basically a Select statement,while Stored Procedure is a sql statement or set of sql statement stored on database server.

6️⃣ What is difference between a Common Table Expression and temporary table?

◼CTE is a temporary result set that is defined within execution scope of a single SELECT ,DELETE,UPDATE statement while temporary table is stored in TempDB and gets deleted once the session expires.

7️⃣ Differentiate between a clustered index and a non-clustered index?

◼ A clustered index determines physical ordering of data in a table and a table can have only one clustered index while a non-clustered index is analogous to index of a book where index is stored at one place and data at other place and index will have pointers to storage location of the data,a table can have more than one non-clustered index.

8️⃣ Explain triggers ?

◼They are sql codes which are automatically executed in response to certain events on a table.They are used to maintain integrity of data.