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✅ Why use HQL? What are its benefits? Answer:HQL (Hibernate Query Language) is designed to let you write object-oriented, database-independent queries over your mapped entities. Its main benefits are: 🔹 1) Works with entities, not tables✅ You write queries using … Continue reading →

🔹 Step-by-step example: 🔹 Key points:✅ FROM User is an HQL statement selecting the entire User entity — no need for SELECT if you want the whole object.✅ session.createQuery(hql, User.class) creates a typed query returning List<User>.✅ Always execute inside an … Continue reading →

No — you don’t have to use SELECT in HQL if you want to fetch entire entities. In HQL, you can simply write: This is equivalent to: Hibernate understands both forms — when you omit SELECT, Hibernate implicitly selects the … Continue reading →

HQL (Hibernate Query Language) is Hibernate’s object-oriented query language that lets you query your database using your Java entity and property names, rather than database table or column names. 🔹 Key points:✅ HQL is similar to SQL in syntax but … Continue reading →

🔹 1️⃣ session.get()✅ Loads the entity immediately from the database or session cache.✅ Returns the real object, not a proxy.✅ Returns null if the entity with the given ID doesn’t exist — safe for optional lookups.✅ Eager behavior → triggers … Continue reading →

You retrieve an object by its primary key (ID) using either:1️⃣ session.get() — recommended for most use cases, or2️⃣ session.load() — advanced use cases. 🔹 Using session.get() Loads the entity immediately from the database or session cache. Returns the entity … Continue reading →

An entity becomes detached (unattached) when it was persistent in a session but is no longer associated with any open session. This happens in several common scenarios: 🔹 1) Session is closed As soon as you call session.close(), all persistent … Continue reading →

You delete an object in Hibernate by:1️⃣ Loading or attaching the entity you want to delete in an active session.2️⃣ Calling session.delete(entity) to mark it for deletion.3️⃣ Committing the transaction to execute the SQL DELETE. 🔹 Example of deleting a … Continue reading →

You get a NonUniqueObjectException if you try to reattach a detached entity using update(), but the session already has another persistent instance with the same identifier (primary key). 🔹 Why does it happen? Hibernate ensures that within a single session, … Continue reading →

There are two main ways to update an object in Hibernate, depending on whether the object is still persistent or has become detached: 🔹 1) Updating a persistent object (easiest case) If the entity is still attached to an open … Continue reading →