leetCode
Vishal Jadhav LEETCODE HotList Questions 📍Arrays and Strings 1. Two Sum (LeetCode 1)2. Longest Substring Without Repeating Characters (LeetCode 3)3. Product of Array Except Self (LeetCode 238)4. Maximum Subarray (LeetCode 53)5. Merge…
Data Engineering
Data Engineer interview.
CAP theorem Lambda vs kapp architecture Star vs snowflake schema Data warehouse , data lake, delta lake, dataware house Scd types SQL How would you write a query to calculate…
partition vs buckting
Difference between Partitioning & bucketing similarity divide the data into many parts and then scan only one part of it. differences partition is a folder and bucket is a file…
pyspark
The following question was asked in the top 10 product-based companies. How would you handle skewed data in PySpark? How to Join Two Large DataFrames in PySpark Efficiently 📌 PySpark…
spark/pyspark performance optimization techniques
best playlist for understanding performance turning narrow(no data shuffling) vs wide(shuffling data across multiple partition ) transformation partitioning and buckting – when we should go with bucket and when shoud…
Surrogate key
Surrogate keys are artificially generated primary keys, typically integers, used to uniquely identify records. In data warehouse you may have same record with multiple entries(this records columns value may change…
SQL Aggregates function – count(), min(), max(), avg(), sum()
SQL also supports the use of aggregate expressions (or functions) that allow you to summarize information about a group of rows of data. Without a specified grouping, each aggregate function…
SQL Joins (anti, self, natural, lnner, left, right, full join)
A JOIN clause is used to query and access data from multiple tables by using logical relationships between them. Join syntax The INNER JOIN is a process that matches rows…
How to delete duplicates from a table
To delete duplicates from a table, you’ll need to identify the duplicate rows first and then delete them using SQL. The approach varies slightly depending on whether you’re working with…
How to find duplicates in a table
Identify duplicates criteria The first step is to define your criteria for a duplicate row. Do you need a combination of two columns to be unique together, or are you…