Q1. Explain the difference between a data lake and a data warehouse.
A data warehouse stores structured, modelled data optimized for analytics and SQL. It uses schema-on-write: data is cleaned and conformed before loading, typically into s...
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Q2. What are the Redis data structures and what is each used for?
Redis exposes several core data types, each with tailored commands. - Strings: counters, cached serialized objects and rate limiters using INCR and SETEX. - Hashes: objec...
Q3. SQL was developed as an integral part of...
Relational Database Management Systems (RDBMS). SQL is the ANSI-standard language for creating, querying, updating, and managing relational databases. Major implementatio...
Q4. What is the difference between a list and a tuple?
- A list is mutable, uses square brackets, and supports append, remove and in-place sorting. - A tuple is immutable, uses parentheses, and once created cannot change. It ...
Q5. What is the difference between ETL and ELT?
ETL extracts data from sources, transforms it on a separate processing engine, then loads the clean result into the target. ELT extracts and loads raw data into the targe...
Q6. When would you embed versus reference documents in MongoDB?
Embed when the child data is always read with the parent, is bounded in size, and belongs to that parent. Reference when the child is large, unbounded, or shared across m...
Q7. What does SQL stand for?
**SQL** stands for **Structured Query Language**. Originally developed at IBM by Donald D. Chamberlin and Raymond F. Boyce in the early 1970s, it was initially named **SE...
Q8. What is the difference between a star schema and a snowflake schema?
Both are dimensional models. A star schema has one central fact table surrounded by denormalized dimension tables. Each dimension is a single table, so joins stay simple ...
Q9. What is a data class and what does it generate?
A `data class` automatically generates `equals()`, `hashCode()`, `toString()`, `copy()` and `componentN()` functions for destructuring, based on the properties declared i...
Q10. What type of language is SQL?
**Declarative (non-procedural)**. You state *what* result you want, not *how* to compute it. The database's **query optimizer** decides the "how" — which indexes to use, ...