Most Asked SQL Interview Questions at MAANG Companies🔥🔥

Preparing for an SQL Interview at MAANG Companies? Here are some crucial SQL Questions you should be ready to tackle:

1. How do you retrieve all columns from a table?

SELECT * FROM table_name;

2. What SQL statement is used to filter records?

SELECT * FROM table_name
WHERE condition;

The WHERE clause is used to filter records based on a specified condition.

3. How can you join multiple tables? Describe different types of JOINs.

SELECT columns
FROM table1
JOIN table2 ON table1.column = table2.column
JOIN table3 ON table2.column = table3.column;

Types of JOINs:

1. INNER JOIN: Returns records with matching values in both tables

SELECT * FROM table1
INNER JOIN table2 ON table1.column = table2.column;

2. LEFT JOIN: Returns all records from the left table & matched records from the right table. Unmatched records will have NULL values.

SELECT * FROM table1
LEFT JOIN table2 ON table1.column = table2.column;

3. RIGHT JOIN: Returns all records from the right table & matched records from the left table. Unmatched records will have NULL values.

SELECT * FROM table1
RIGHT JOIN table2 ON table1.column = table2.column;

4. FULL JOIN: Returns records when there is a match in either left or right table. Unmatched records will have NULL values.

SELECT * FROM table1
FULL JOIN table2 ON table1.column = table2.column;

4. What is the difference between WHERE & HAVING clauses?

WHERE: Filters records before any groupings are made.

SELECT * FROM table_name
WHERE condition;

HAVING: Filters records after groupings are made.

SELECT column, COUNT(*)
FROM table_name
GROUP BY column
HAVING COUNT(*) > value;

5. How do you calculate average, sum, minimum & maximum values in a column?

Average: SELECT AVG(column_name) FROM table_name;

Sum: SELECT SUM(column_name) FROM table_name;

Minimum: SELECT MIN(column_name) FROM table_name;

Maximum: SELECT MAX(column_name) FROM table_name;

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

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Hope it helps :)

Want to make a transition to a career in data?

Here is a 7-step plan for each data role

Data Scientist

Statistics and Math: Advanced statistics, linear algebra, calculus.
Machine Learning: Supervised and unsupervised learning algorithms.
xData Wrangling: Cleaning and transforming datasets.
Big Data: Hadoop, Spark, SQL/NoSQL databases.
Data Visualization: Matplotlib, Seaborn, D3.js.
Domain Knowledge: Industry-specific data science applications.

Data Analyst

Data Visualization: Tableau, Power BI, Excel for visualizations.
SQL: Querying and managing databases.
Statistics: Basic statistical analysis and probability.
Excel: Data manipulation and analysis.
Python/R: Programming for data analysis.
Data Cleaning: Techniques for data preprocessing.
Business Acumen: Understanding business context for insights.

Data Engineer

SQL/NoSQL Databases: MySQL, PostgreSQL, MongoDB, Cassandra.
ETL Tools: Apache NiFi, Talend, Informatica.
Big Data: Hadoop, Spark, Kafka.
Programming: Python, Java, Scala.
Data Warehousing: Redshift, BigQuery, Snowflake.
Cloud Platforms: AWS, GCP, Azure.
Data Modeling: Designing and implementing data models.

#data

This is how ML works

Here's a concise cheat sheet to help you get started with Python for Data Analytics. This guide covers essential libraries and functions that you'll frequently use.


1. Python Basics
- Variables:
x = 10
y = "Hello"

- Data Types:
  - Integers: x = 10
  - Floats: y = 3.14
  - Strings: name = "Alice"
  - Lists: my_list = [1, 2, 3]
  - Dictionaries: my_dict = {"key": "value"}
  - Tuples: my_tuple = (1, 2, 3)

- Control Structures:
  - if, elif, else statements
  - Loops: 
  

    for i in range(5):
        print(i)
    

  - While loop:
  

    while x < 5:
        print(x)
        x += 1
    

2. Importing Libraries

- NumPy:

  import numpy as np
  

- Pandas:

  import pandas as pd
  

- Matplotlib:

  import matplotlib.pyplot as plt
  

- Seaborn:

  import seaborn as sns
  

3. NumPy for Numerical Data

- Creating Arrays:

  arr = np.array([1, 2, 3, 4])
  

- Array Operations:

  arr.sum()
  arr.mean()
  

- Reshaping Arrays:

  arr.reshape((2, 2))
  

- Indexing and Slicing:

  arr[0:2]  # First two elements
  

4. Pandas for Data Manipulation

- Creating DataFrames:

  df = pd.DataFrame({
      'col1': [1, 2, 3],
      'col2': ['A', 'B', 'C']
  })
  

- Reading Data:

  df = pd.read_csv('file.csv')
  

- Basic Operations:

  df.head()          # First 5 rows
  df.describe()      # Summary statistics
  df.info()          # DataFrame info
  

- Selecting Columns:

  df['col1']
  df[['col1', 'col2']]
  

- Filtering Data:

  df[df['col1'] > 2]
  

- Handling Missing Data:

  df.dropna()        # Drop missing values
  df.fillna(0)       # Replace missing values
  

- GroupBy:

  df.groupby('col2').mean()
  

5. Data Visualization

- Matplotlib:

  plt.plot(df['col1'], df['col2'])
  plt.xlabel('X-axis')
  plt.ylabel('Y-axis')
  plt.title('Title')
  plt.show()
  

- Seaborn:

  sns.histplot(df['col1'])
  sns.boxplot(x='col1', y='col2', data=df)
  

6. Common Data Operations

- Merging DataFrames:

  pd.merge(df1, df2, on='key')
  

- Pivot Table:

  df.pivot_table(index='col1', columns='col2', values='col3')
  

- Applying Functions:

  df['col1'].apply(lambda x: x*2)
  

7. Basic Statistics

- Descriptive Stats:

  df['col1'].mean()
  df['col1'].median()
  df['col1'].std()
  

- Correlation:

  df.corr()
  

This cheat sheet should give you a solid foundation in Python for data analytics. As you get more comfortable, you can delve deeper into each library's documentation for more advanced features.

I have curated the best resources to learn Python 👇👇
https://whatsapp.com/channel/0029VaiM08SDuMRaGKd9Wv0L

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If you are interested to learn SQL for data analytics purpose and clear the interviews, just cover the following topics

1)Install MYSQL workbench
2) Select
3) From
4) where
5) group by
6) having
7) limit
8) Joins (Left, right , inner, self, cross)
9) Aggregate function ( Sum, Max, Min , Avg)
9) windows function ( row num, rank, dense rank, lead, lag, Sum () over)
10)Case
11) Like
12) Sub queries
13) CTE
14) Replace CTE with temp tables
15) Methods to optimize Sql queries
16) Solve problems and case studies at Ankit Bansal youtube channel

Trick: Just copy each term and paste on youtube and watch any 10 to 15 minute on each topic and practise it while learning , By doing this , you get the basics understanding

17) Now time to go on youtube and search data analysis end to end project using sql

18) Watch them and practise them end to end.

17) learn integration with power bi

In this way , you will not only memorize the concepts but also learn how to implement them in your current working and projects and will be able to defend it in your interviews as well.

Like for more

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

Hope it helps :)