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- SQL.How can you compare two nullable values safely, and how does IS DISTINCT FROM differ from <>?
- SQL.How are NULL values ordered by ORDER BY, how do defaults differ between databases, and how can you control their placement?
- SQL.How does NULL propagate through arithmetic expressions, and how can COALESCE and NULLIF help handle missing values and division by zero?
- SQL.How does NULL affect join conditions, and why can filtering the right-hand table in WHERE remove unmatched rows from a LEFT JOIN?
- SQL.How do GROUP BY and DISTINCT treat NULL values, even though NULL = NULL evaluates to UNKNOWN?
- SQL.How do aggregate functions handle NULL, and what is the difference between COUNT(*), COUNT(column), and COUNT(DISTINCT column)?
- SQL.How does NULL affect IN and NOT IN, and why can NOT EXISTS be a safer choice when a subquery returns nullable values?
- SQL.How do WHERE, HAVING, and CHECK constraints treat conditions that evaluate to UNKNOWN?
- SQL.Why do column = NULL and column <> NULL not work as expected, and when should you use IS NULL and IS NOT NULL?
- SQL.What is SQL’s three-valued logic (TRUE, FALSE, UNKNOWN), and how do AND, OR, and NOT behave with UNKNOWN?
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- SQL.What are domain types (or constraints on data types), and how do they help enforce data correctness?
- SQL.How does SQL handle comparisons between different data types (for example, string vs number), and why is this dangerous?
- SQL.What is the difference between DATE, TIME, TIMESTAMP, and TIMESTAMPTZ, and which one should be used for business events?
- SQL.How do numeric types like INTEGER, BIGINT, DECIMAL, and FLOAT differ in terms of precision and use cases?
- SQL.What problems can arise from implicit type casting in SQL, and how can it affect indexes?
- SQL.How does NULL differ from 0, an empty string, or FALSE in SQL?
- SQL.What is the difference between CHAR, VARCHAR, and TEXT, and when would you choose each?
- SQL.What is MVCC ?
- SQL.What is AutoVacuum Postgres ?
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Category Archives: Без рубрики
Java.Reactive.What is the role of Subscription in reactive programming?
the Subscription plays a pivotal role in managing flow control and resource management in reactive programming. Let’s break it down 👇 🎯 What is a Subscription? In Reactive Streams (Java 9 Flow API, RxJava, Reactor, Akka Streams), a Subscription is … Continue reading
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Java.Reactive.Tell me about RxJava, Project Reactor, Spring WebFlux, Akka Streams. Lets look at one simple example written on each of that libs with cold and hot subscription ?
Let’s compare RxJava, Project Reactor, Spring WebFlux, and Akka Streams, each with simple Cold vs Hot observable examples.
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Java.Multithreading.What is java reactive flow ?
Java Reactive Flow, which is part of the Reactive Streams specification — the foundation of modern reactive libraries like RxJava, Project Reactor, and Akka Streams. 🌊 What is Java Reactive Flow? ✅ It’s a standard API introduced in Java 9 … Continue reading
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Java.Reactive.Explain the difference between Hot and Cold Observable
Understanding the difference between Hot and Cold Observables is crucial to mastering RxJava and reactive programming in general — especially when working with time-sensitive or shared data sources. Let’s break it down clearly and visually 👇 ❄️ Cold Observable 📌 … Continue reading
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Java.Reactive.🎯 Who is the Consumer in Reactive Programming?
🧠 Summary Backpressure = “Slow down! I can’t handle that much data right now!” Prevents overwhelming the consumer. Crucial for building robust, scalable, and memory-safe reactive systems. In a reactive stream, the consumer is the Observer / Subscriber — the … Continue reading
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Java.Reactive.What is backpressure in the context of reactive programming?
🙌 Backpressure is one of the most important — and often misunderstood — concepts in reactive programming, especially when dealing with asynchronous streams. Let’s unpack it clearly 👇 🔄 What is Backpressure? Backpressure refers to a situation and a mechanism … Continue reading
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Java.Reactive.Describe the role of Observable and Observer in reactive programming
🎯 Goal of Reactive Programming: To react to a stream of data/events over time, in a non-blocking, asynchronous, and declarative way. This is achieved by two main players: 🧩 1. Observable<T> — The Data Source ✅ What it is: An … Continue reading
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Java.Reactive.What is the Observer pattern and how does it underlie reactive programming?
The Observer Pattern is a behavioral design pattern where: One object (the Subject) maintains a list of Observers. When the Subject’s state changes, it notifies all its Observers. Think of it like a subscription model: You (Observer) subscribe to a … Continue reading
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Java.Reactive.How Many Threads Can You Have in RxJava?
📌 It depends on the Scheduler you use. ✅ Schedulers.io() Purpose: For I/O-bound tasks like DB calls, file access, HTTP calls. Type: Cached thread pool (like Java’s Executors.newCachedThreadPool()). Threads: Unbounded (new threads created as needed, idle ones reused). Good for: … Continue reading
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Java.Reactive. observeOn(Schedulers.io()) — What does it really do?
This line changes the thread where the subscriber and everything downstream of it will run. 🔧 The Reactive Pipeline Has Stages Imagine this code: Here’s what happens: just(“Stanley”) emits the data. .map(…) transforms it (runs on the same thread as … Continue reading
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