Q141. What is the difference between DELETE, TRUNCATE and DROP?
These three remove data at very different levels. `DELETE FROM t WHERE ...` is DML. It removes selected rows, fires triggers, is fully logged, can be rolled back within a...
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Q142. Compare the OSI model and the TCP/IP model.
The OSI model is a seven-layer reference model: Physical, Data Link, Network, Transport, Session, Presentation and Application. The TCP/IP model as taught is four layers:...
Q143. What are the main responsibilities of an operating system?
An operating system manages hardware and provides abstractions so programs do not talk to devices directly. Its main responsibilities are: - Process management: create, s...
Q144. What is encapsulation and why does it matter?
Encapsulation means bundling data with the operations that act on it and restricting direct access to the internals. The class exposes a deliberate public API and keeps f...
Q145. What is a funnel analysis and how do you build one?
A funnel measures how many users progress through an ordered sequence of steps, such as view, add to cart, checkout and purchase. The conversion rate at each step shows w...
Q146. What are Type I and Type II errors?
A Type I error is a false positive: rejecting the null hypothesis when it is actually true. Its probability is the significance level alpha, usually 0.05. In a fraud syst...
Q147. How do you handle class imbalance in a classification problem?
Class imbalance means one class is far rarer, so accuracy becomes misleading and models favor the majority. Strategies: - Resampling: oversample the minority (SMOTE synth...
Q148. 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 ...
Q149. Explain key expiry and eviction policies in Redis.
You set a time to live with EXPIRE, SETEX or PEXPIRE. Redis removes expired keys lazily on access and also runs a background sampling cycle that actively deletes expired ...
Q150. How do indexes work in MongoDB and what is a compound index?
An index is a B-tree structure storing a sorted subset of a collection's fields, letting the planner find documents without scanning everything. Without an index a query ...