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Database Articles
Page 113 of 547
Find objects between two dates in MongoDB?
Use the $gte (greater than or equal) and $lt (less than) operators with ISODate() to find documents between two dates in MongoDB. Create Sample Data db.order.insertMany([ {"OrderId": 1, "OrderAddress": "US", "OrderDateTime": ISODate("2019-02-19")}, {"OrderId": 2, "OrderAddress": "UK", "OrderDateTime": ISODate("2019-02-26")}, {"OrderId": 3, "OrderAddress": "IN", "OrderDateTime": ISODate("2019-03-05")} ]); Find Between Two Dates Find orders between Feb 10 and Feb 21 ? db.order.find({ "OrderDateTime": { $gte: ISODate("2019-02-10"), ...
Read MoreUpdate MongoDB field using value of another field?
In MongoDB, you can update a field using the value of another field in the same document. There are two main approaches − using the aggregation pipeline with $set (MongoDB 4.2+) or using $addFields with $out for writing results to a collection. Method 1: Update with Aggregation Pipeline (MongoDB 4.2+) Use updateMany() with an aggregation pipeline to set a field based on other fields ? // Create sample data db.studentInformation.insertOne({ "StudentFirstName": "Carol", "StudentLastName": "Taylor" }); // Update: create FullName from FirstName + LastName db.studentInformation.updateMany( ...
Read MoreRetrieve only the queried element in an object array in MongoDB collection?
To retrieve only the matching element from an object array in MongoDB, use the $elemMatch projection operator or the $ positional projection operator. Both return only the first array element that matches the query condition. Create Sample Data db.objectArray.insertMany([ { "Persons": [ {"PersonName": "Adam", "PersonSalary": 25000}, {"PersonName": "Larry", "PersonSalary": 27000} ] ...
Read MoreOpen Source Databases
Open source databases have publicly available source code that anyone can view, study, or modify. They can be relational (SQL) or non-relational (NoSQL), and they significantly reduce database costs compared to proprietary solutions. Why Use Open Source Databases? Database licensing is a major software expense for companies. Open source databases offer a cost-effective alternative − free to use, with community support, and no vendor lock-in. Many also offer commercial support tiers for enterprise needs. Popular Open Source Databases Database Type Key Feature MySQL Relational (SQL) Most widely used open source DB; community ...
Read MoreHow to Download and Install PostgreSQL on Windows?
PostgreSQL is a powerful, open-source relational database system used for enterprise applications. This guide covers downloading, installing, configuring, and testing PostgreSQL on Windows. Downloading PostgreSQL Go to postgresql.org/download/windows Click Download the installer (EnterpriseDB graphical installer) Select the latest version for your OS (64-bit recommended) Download will begin automatically Installing PostgreSQL Run the downloaded installer and follow these steps − Step 1: Welcome screen → Click Next Step 2: Select components (keep all selected: PostgreSQL Server, pgAdmin, Command Line Tools, Stack Builder) Step 3: Choose installation directory (default recommended) Step 4: Choose data ...
Read MoreOverview of Dynamic Partition in Hive
Apache Hive is a data warehousing system built on Hadoop for analytics and MapReduce jobs. Partitioning divides large datasets into smaller parts for faster queries. Dynamic partitioning automatically determines partition values from the data being inserted, unlike static partitioning where values are manually specified. Static vs Dynamic Partitioning Feature Static Partitioning Dynamic Partitioning Partition values Manually specified per insert Automatically derived from data Best for Few known partitions Many or unknown partitions WHERE clause Required Not required Flexibility Low High Enabling Dynamic Partitioning ...
Read MoreOracle Label-Based Security
Oracle Label-Based Security (OLS) provides fine-grained, row-level access control based on security labels. Each row of data is assigned a sensitivity label (e.g., Confidential, Secret, Top Secret), and each user is assigned a clearance level. Users can only access data where their clearance meets or exceeds the data's sensitivity. How OLS Works User Clearance: SECRET ...
Read MoreOperations on Files
When working with files in a DBMS, two fundamental types of operations are performed: retrieval (finding and reading records) and update (inserting, deleting, or modifying records). Both use selection conditions to identify target records. Selection Conditions A selection condition specifies criteria that records must meet. Conditions can be − Simple − Uses one field (e.g., Ssn = '123-45-6789') Complex − Combines multiple fields with comparison operators (e.g., Department = 'Sales' AND Salary ≥ 30000) File Operations The typical sequence of file operations − 1. Open file 2. Find first record matching ...
Read MoreOLAP Operations in DBMS
OLAP (Online Analytical Processing) enables users to perform multidimensional analysis on data organized into cubes (hypercubes). Each cell in a cube corresponds to a specific combination of dimension values (e.g., Location → Time → Product). OLAP uses pre-aggregation and indexing for fast querying. Types of OLAP Servers Type Storage Trade-off ROLAP Relational database (SQL queries) Handles large data, slower queries MOLAP Multidimensional arrays Fast queries, limited data size HOLAP Hybrid (ROLAP + MOLAP) Scalability + speed balance OLAP Operations ...
Read MoreObject Database Conceptual Design
An object database stores data as objects (containing both data and methods), working directly with object-oriented programming languages like Java and Python. Object-oriented modeling supports inheritance, encapsulation, and polymorphism, making it more flexible than the traditional relational model for complex relationships. ODB vs RDB Conceptual Design Feature Object Database (ODB) Relational Database (RDB) Relationships OID references (single or collections) Matching attribute values (foreign keys) Inheritance Built-in (extends, derives) No built-in construct Operations Part of class definition, specified early Can be delayed to implementation Multivalued Attributes Supported (set, bag, ...
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