Database Management Systems: Purpose, Functions, and Scope

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Database Management Systems: Purpose, Functions, and Scope

System Analysis and Design · Chapter 6: Database Design, Normalization, and Business IntelligenceSection 6.2 · lesson 40 of 696 min · free with a free account

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In this lesson

What a DBMS does, SQL's two roles, and relational vs. NoSQL.

  • Explain what a DBMS is and its 4 core functions
  • Distinguish SQL's Data Definition Language from its Data Manipulation Language
  • Compare relational and NoSQL database management systems
  • Identify common examples of each type

Transcript

Everything said in the video, section by section (787 words). Read along, or search it.

Database Design, Normalization, and Business Intelligence

Database Management Systems

The last section introduced the database approach, with a D B M S managing shared data. This section looks at the D B M S itself. What it does, the two roles of the SQL language, and the two broad families of database systems in use today.

Figure 1

The Layer Between Applications and Data

A database management system, or D B M S, is software that sits between an application and the raw data it depends on. In this picture, a web app, a mobile app, and a reporting tool all need the same data. None of them touches the stored data directly. Every request passes through the D B M S in the middle. Why structure things this way? Because otherwise every application would reinvent how to store, protect, and retrieve data safely. The D B M S provides that layer once, so developers can rely on it instead of building it themselves.

What It Provides

4 Core Functions

Four functions make up the core of what a D B M S provides. Storage management organizes data efficiently on disk. It maintains indexes, so records can be found quickly, rather than scanned one by one. Security controls who can view or change data, through authentication, and permissions assigned to specific users or roles. Concurrency control manages many users or programs accessing and changing data at the same time. Without it, one user's change could silently overwrite another's. And backup and recovery protects against data loss from hardware failure or human error. It restores the database to a consistent state afterward.

SQL's 2 Roles

DDL and DML

SQL, or structured query language, is the standard language for working with a relational database. Its commands fall into two distinct roles that are easy to confuse. Data definition language, or D D L, includes create, alter, and drop. It defines or changes the structure of the database itself, such as creating a new table, or adding a column. Data manipulation language, or D M L, includes select, insert, update, and delete. It works with the data that already lives inside an existing structure, such as retrieving or changing rows. Here is a simple way to keep them straight. D D L changes the shape of the container. D M L changes what is inside it.

Seeing the Difference

One DDL Statement, One DML Statement

Here are the two, side by side. Create table students defines a new structure. That is D D L. It says nothing about any particular student. It builds the container. Select star from students, where G P A is greater than three point five, works with data already stored in that structure. That is D M L. It reads what is inside the container. One statement shapes the database. The other uses it.

2 Families

Relational vs. NoSQL

Not every D B M S organizes data the same way. Two broad families are in wide use. Relational databases store data in tables, with a fixed schema of rows and columns. NoSQL databases use flexible structures, such as documents, key-value pairs, or graphs. Relational databases share a standard query language, SQL. NoSQL query languages vary by product, with no single shared standard. Relational databases fit structured data with clear, stable relationships. NoSQL fits large-scale, rapidly changing, or loosely structured data. And relational databases offer strong consistency, through ACID transactions. NoSQL systems often favor availability and scale, sometimes with only eventual consistency.

In the Real World

Common Database Systems

Here are some common examples. MySQL is relational, and widely used for web applications. PostgreSQL is relational, chosen for advanced features and strict standards compliance. Oracle Database is relational, and common in large-scale enterprise systems. Microsoft SQL Server is relational, often used in Windows-based enterprise environments. MongoDB is a NoSQL document database, suited to flexible or frequently changing data structures. And Redis is a NoSQL key-value store, used for caching and real-time applications.

Key Terms

The Vocabulary of This Section

Let's lock in the key terms. A D B M S is software that manages how data is stored, secured, and retrieved on behalf of applications. D D L is the set of SQL commands that define or change a database's structure. D M L is the set of SQL commands that work with data inside an existing structure. Concurrency control is the function that manages simultaneous access to data by many users or programs. And NoSQL is a category of database systems that do not require a fixed table schema.

Key Takeaways

What to Carry Forward

To pull this together. A D B M S provides four core functions. Storage management, security, concurrency control, and backup and recovery. SQL's D D L commands define or change a database's structure, while its D M L commands work with the data inside it. Relational databases use a fixed table schema and strong consistency. NoSQL databases trade that structure for flexibility and scale. And common relational systems include MySQL, PostgreSQL, Oracle Database, and SQL Server, while common NoSQL systems include MongoDB and Redis.

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Where the credit goes

Universities that work with NCCRS

System Analysis and Design carries a NCCRS credit recommendation. These universities work with NCCRS; some are UPI Study's signed partners. ACE and NCCRS have over 2,100 cooperating colleges that will consider accepting credits; the final decision is with the universities.

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FAQ

Questions students ask us

About Database Management Systems: Purpose, Functions, and Scope

What are the core functions of a database management system?
A database management system (DBMS) provides four core functions: storage management, security, concurrency control, and backup and recovery. Storage management organizes data on disk and maintains indexes for fast lookups. Security controls who can view or change data through authentication and permissions. Concurrency control manages simultaneous access so one user's change does not silently overwrite another's. Backup and recovery restores a consistent state after failures or errors.
What is the difference between DDL and DML in SQL?
Data definition language (DDL) defines or changes the structure of a database, while data manipulation language (DML) works with the data inside that structure. DDL includes CREATE, ALTER, and DROP, such as CREATE TABLE students. DML includes SELECT, INSERT, UPDATE, and DELETE, such as selecting students with a GPA above 3.5. A simple way to remember: DDL shapes the container, and DML changes what is inside it.
What is the difference between relational and NoSQL databases?
Relational databases store data in tables with a fixed schema and share a standard query language, SQL, while NoSQL databases use flexible structures such as documents, key-value pairs, or graphs, with query languages that vary by product. Relational systems suit structured data with stable relationships and offer strong consistency through ACID transactions. NoSQL suits large-scale or loosely structured data and often favors availability and scale.
What are some examples of relational and NoSQL database systems?
Common relational database systems include MySQL, widely used for web applications, PostgreSQL, known for advanced features and standards compliance, Oracle Database, common in large enterprises, and Microsoft SQL Server. Common NoSQL systems include MongoDB, a document database suited to flexible or frequently changing data structures, and Redis, a key-value store often used for caching and real-time applications.

About the System Analysis and Design course

How many college credits is System Analysis and Design?
System Analysis and Design (Computer Science 390) carries a NCCRS credit recommendation for 3 semester credits. ACE and NCCRS have over 2,100 cooperating colleges that will consider accepting credits; the final decision is with the universities.
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UPI Study has signed partner agreements with universities such as Thomas Edison State University, University of the People and Charter Oak State College, and works with universities such as Penn State, SNHU and SUNY. ACE and NCCRS have over 2,100 cooperating colleges that will consider accepting credits; the final decision is with the universities. Use "Find my college" on this page to check yours.
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