DatabasesLesson 1 of 1 in the course Relational model and SQL

SQL Foundations: Language Model, History, Types, and Semantics

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

SQL is the widely used language for working with structured data in relational database systems. This lesson introduces what SQL is, how it differs from older data-access approaches, and the main kinds of work it supports.

Structured Query Language (SQL) is a domain-specific language used to manage data, especially data stored in a relational database management system (RDBMS). Relational databases organize structured information in tables and represent relationships among entities and variables.

All flashcards

What is SQL?
Structured Query Language is a domain-specific language for managing data, especially in relational database systems.
What does set-oriented access mean in SQL?
A single command can access or affect many records rather than requiring a separate operation for each one.
How do DDL and DML differ?
DDL defines or modifies database structures; DML inserts, updates, or deletes stored data.
What does it mean that SQL is primarily declarative?
Users state the desired data operation or result, and the database determines how to carry it out.
What does NULL represent in SQL?
NULL marks the absence of a value; it is distinct from zero and an empty string.

Quiz questions

  1. Who developed an early version of SQL for IBM’s System R?Answer: Donald D. Chamberlin and Raymond F. Boyce.
  2. Which pair gives the years when ANSI and ISO first adopted SQL as a standard, in that order?Answer: ANSI 1986; ISO 1987.
  3. Which set consists entirely of constructed SQL types?Answer: ARRAY, MULTISET, REF, and ROW.
  4. What does IBM’s Distributed Relational Database Architecture (DRDA) enable?Answer: Connected relational databases to cooperate on SQL requests.
  5. In SQL, what can an ordinary comparison involving NULL evaluate to?Answer: Unknown, as part of SQL’s three-valued logic.

Based on the Wikipedia article SQL, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.

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