Many-to-many relationships can be implemented using a junction table with the keys from both the tables forming the composite primary key of the junction table.īring out the difference between a primary key and a unique key.īoth primary key and unique key enforce the uniqueness of the column on which they are defined. The one-to-many relationship can be implemented by splitting the data into two tables with primary and foreign key relationships. The one-to-one relationship can be implemented as a single table and very rarely as two tables with primary and foreign key relationships. How do you implement one-to-one, one-to-many, and many-to-many relationships while designing tables? Security: A DBMS can restrict the reading/writing of data to authorized users only.The DBMS keeps the fragmented data consistent. Data distribution: You can partition data across various sites, organizations, and hardware platforms.Data quality: You can specify rules that data must satisfy.Multiple application programs can read/write data to the same database. Sharing between users & sharing between applications: Multiple users can access the database at the same time.Efficiency: A DBMS has efficient algorithms for managing large quantities of data.Data Protection: A DBMS protects data from accidental loss due to hardware crashes, disk media failures, and application errors.Some of the reasons for using a DBMS are:. A database contains the data structure or ‘schema’ – description of data - as well as the data.Ī database management system (DBMS) is the software for managing access to a database. Self-description is what sets a database apart from ordinary files. Java J2EE Interview Questions on Databases & JdbcĪ database is a permanent, self-descriptive store of data that is contained in one or more files. We have compiled most frequently asked Java J2EE Interview Questions which will help you with different expertise levels.
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