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Week 2

2.4 Database Languages

DBMS provides several languages for interacting with the database:

1.      Data Definition Language (DDL) — Defines the database structure. Commands: CREATE, ALTER, DROP, TRUNCATE

2.      Data Manipulation Language (DML) — Manipulates data. Commands: SELECT, INSERT, UPDATE, DELETE

3.      Data Control Language (DCL) — Controls access. Commands: GRANT, REVOKE

4.      Transaction Control Language (TCL) — Manages transactions. Commands: COMMIT, ROLLBACK, SAVEPOINT

SQL (Structured Query Language) is the industry-standard language that combines DDL, DML, DCL, and TCL into one integrated language. It is used by virtually all relational DBMS products.

Database Roles and People

Role

Responsibilities

Database Administrator (DBA)

Responsible for the overall health of the database — installation, configuration, performance tuning, security, backup/recovery, user management.

Database Designer

Designs the structure of the database — identifies entities, relationships, attributes, and constraints.

Application Developer

Builds applications that use the database. Writes SQL queries and application code.

Naive End User

Uses applications (like a bank teller's terminal) without knowing SQL or the database structure.

Sophisticated End User

Directly queries the database using SQL (e.g., a data analyst at Access Bank).

 

Reading List / References

Connolly, T. & Begg, C. (2015). Database Systems, Chapters 2 & 3: Database Architecture. Pearson.

Silberschatz, A. et al. (2020). Database System Concepts, Chapter 1: Overview. McGraw-Hill.

ANSI/X3/SPARC Study Group on DBMS (1975). Interim Report. FDT Bulletin, 7(2).

Activities

Self-Assessment Quiz: 1. Name the FIVE components of a database system. 2. What is the difference between the external and conceptual schema in the three-schema architecture? 3. Define physical data independence and give an example. 4. What is the difference between DDL and DML? Give ONE command from each.

 

Lab Exercise: Install MySQL Workbench (or use an online SQL tool like SQLFiddle). Create a new schema called 'university_db'. Create a simple STUDENT table with columns: student_id (INT, PRIMARY KEY), first_name (VARCHAR 50), last_name (VARCHAR 50), department (VARCHAR 50), level (INT). Insert 5 sample student records. Screenshot your work for submission.