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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?
- ChromeDevTools.Watch all failed requests
- 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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Author Archives: Stanislav_Panteleev
Java.Hibernate.Beginner.What is a Hibernate mapping file?
✅ What is a Hibernate mapping file? Answer:A Hibernate mapping file is an XML file (usually ending with .hbm.xml) that tells Hibernate how to map a Java class to a database table, and how the class’s fields map to table … Continue reading
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Java.Hibernate.Beginner.What is a Configuration object in Hibernate?
✅ What is a Configuration object in Hibernate? Answer:A Configuration object in Hibernate is a class that loads and holds all the settings, mappings, and properties required to bootstrap Hibernate and build a SessionFactory. 🔹 Key responsibilities of Configuration: Reads … Continue reading
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Java.Hibernate.Beginner.What about Session Fatory in Spring Boot ?
In Spring Boot, you don’t usually build or manage a SessionFactory manually. Instead, Spring Boot autoconfigures Hibernate and manages the SessionFactory for you, thanks to its integration with Spring Data JPA or the Hibernate starter. 🔹 How it works in … Continue reading
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Java.Hibernate.Beginner.What is a SessionFactory?
✅ What is a SessionFactory in Hibernate? Answer:A SessionFactory is a heavyweight, thread-safe Hibernate object responsible for: Creating Session instances, which are the primary interface for interacting with the database. Managing configuration settings like database connection details, entity mappings, and … Continue reading
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Java.Hibernate.Beginner.What is a Session in Hibernate?
Excellent — here’s a clear, interview-level answer: ✅ What is a Session in Hibernate? Answer:A Session in Hibernate is the primary interface between your Java application and the database. It represents a single unit of work (a conversation with the … Continue reading
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Java.Hibernate.Beginner.What are the main advantages of using Hibernate?
✅ What are the main advantages of using Hibernate? Answer:Hibernate offers several major advantages over plain JDBC or manual SQL, making it one of the most popular Java persistence frameworks: 🔹 1. Reduces Boilerplate Code Automates most CRUD operations — … Continue reading
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Java.Hibernate.Beginner.What is ORM?
ORM stands for Object-Relational Mapping — a programming technique that automatically maps objects in your application code to rows in a relational database table, and vice versa. 🔹 How it works: You define Java (or any language’s) classes called entities, … Continue reading
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Java.Hibernate.Beginner.Why do we use Hibernate instead of JDBC?
Excellent — this is a classic beginner question, and here’s a strong interview-level answer: ✅ Why do we use Hibernate instead of JDBC? Answer:Hibernate offers a higher-level, object-oriented way of interacting with databases compared to plain JDBC, which requires a … Continue reading
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Java.Hibernate.Beginner.Which connection pool hibernte uses ?
✅ How does Hibernate handle database connections? Does it use HikariCP under the hood? Answer:🔹 How Hibernate manages connections: Hibernate doesn’t open raw database connections manually each time you run a query. Instead, it uses a connection pool to efficiently … Continue reading
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Java.Hibernate.Beginner.What is Hibernate?
Hibernate is an Object-Relational Mapping (ORM) framework for Java that lets developers map Java objects (entities) to relational database tables. It abstracts away the boilerplate JDBC code needed for CRUD operations. Provides a powerful query language (HQL) and Criteria API. … Continue reading
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