Database Design Fundamentals

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

This ensures that the column always has a ______,

value

Which can be useful for maintaining data ______ and enforcing business rules.

integrity

This process is important for ______ business rules.

enforcing

A defined value in the column ensures ______ in the dataset.

<p>consistency</p> Signup and view all the answers

Data ______ is essential for creating reliable reports.

<p>integrity</p> Signup and view all the answers

To create a unique constraint, specify the column to be ______.

<p>constrained</p> Signup and view all the answers

The unique constraint command uses the format UNIQUE (______).

<p>column_name</p> Signup and view all the answers

An example of adding a unique constraint would be ALTER TABLE person ADD CONSTRAINT phone_unique UNIQUE(______).

<p>phone</p> Signup and view all the answers

The command adds a unique constraint named phone_unique to the ______ column.

<p>phone</p> Signup and view all the answers

In SQL, a unique constraint prevents duplicate values in a specified ______.

<p>column</p> Signup and view all the answers

The ______ keyword defines a unique constraint.

<p>unique</p> Signup and view all the answers

Using unique constraints helps prevent ______ data and maintain data integrity.

<p>duplicate</p> Signup and view all the answers

It is important to carefully consider the unique ______ you create for a table.

<p>constraints</p> Signup and view all the answers

Unique constraints help maintain data ______.

<p>integrity</p> Signup and view all the answers

Creating unique constraints can prevent issues related to ______ data.

<p>duplicate</p> Signup and view all the answers

The INSERT command is used to add new rows to a ______.

<p>table</p> Signup and view all the answers

The syntax for the INSERT command includes INSERT INTO ______ (column1, column2, ...).

<p>table_name</p> Signup and view all the answers

In the example, the new row is inserted into the 'person' table with the value for 'fname' as ______.

<p>Ali</p> Signup and view all the answers

The VALUES clause in the INSERT command must match the order of the ______ specified.

<p>columns</p> Signup and view all the answers

The ALTER TABLE command is used to ______ a table.

<p>rename</p> Signup and view all the answers

Inserting a new row into the 'person' table also includes a value for 'salary' as ______.

<p>450</p> Signup and view all the answers

To add a new column, use the add column ______ followed by the column name.

<p>clause</p> Signup and view all the answers

The add column clause requires the ______ type.

<p>data</p> Signup and view all the answers

You can also add ______ when modifying a table.

<p>constraints</p> Signup and view all the answers

The command ALTER TABLE allows you to ______ existing columns.

<p>modify</p> Signup and view all the answers

char(10) reserves 10 bytes of memory for a string, even if it contains fewer ______.

<p>characters</p> Signup and view all the answers

A varchar(n) data type is used for a ______ length string.

<p>variable</p> Signup and view all the answers

The varchar(n) data type only uses the actual space needed for the ______.

<p>content</p> Signup and view all the answers

char reserves a fixed amount of memory, while varchar uses ______ storage.

<p>variable</p> Signup and view all the answers

varchar(n) reserves space for a string of specified length but utilizes only the ______ needed.

<p>actual space</p> Signup and view all the answers

Flashcards

Default Value

A feature in databases that automatically assigns a value to a column if it is empty.

Data Integrity

The practice of ensuring data in a database conforms to predefined rules and standards.

Data Validation

A technique to prevent errors and inconsistencies in a table's data.

Business Rules

Rules that dictate acceptable values within a database.

Signup and view all the flashcards

Why is a default value useful?

A default value ensures a column never remains empty, promoting data consistency and reliability.

Signup and view all the flashcards

String

A data type that stores text information. It can contain letters, numbers, symbols, and spaces.

Signup and view all the flashcards

VARCHAR

A data type that stores a variable-length string of characters. It only uses the necessary space for the actual data.

Signup and view all the flashcards

CHAR

A data type that stores a fixed-length string of characters. It reserves a specific number of bytes regardless of the actual data length.

Signup and view all the flashcards

n in VARCHAR(n)

The maximum number of characters that the data type can store.

Signup and view all the flashcards

Reserve memory

To reserve a specific amount of memory for a data type, even if it is not fully used.

Signup and view all the flashcards

Unique Constraint

A database constraint that ensures each value in a column is unique, preventing duplicate entries.

Signup and view all the flashcards

UNIQUE keyword

A database keyword that creates a unique constraint for a column, ensuring uniqueness.

Signup and view all the flashcards

Maintaining Data Integrity

The process of preserving the accuracy and consistency of data, preventing errors and inconsistencies.

Signup and view all the flashcards

Careful Consideration of Unique Constraints

Carefully choosing the appropriate unique constraints helps ensure data accuracy and avoids unnecessary restrictions.

Signup and view all the flashcards

Preventing Duplicate Data

Duplicate data can create inconsistencies and errors, leading to unreliable information.

Signup and view all the flashcards

ALTER TABLE

An SQL command used to modify the structure of an existing table.

Signup and view all the flashcards

ADD COLUMN

The clause used within an ALTER TABLE command to add a new column to an existing table.

Signup and view all the flashcards

Data Type

The data type specifies the kind of data a column can hold, such as text, numbers, or dates.

Signup and view all the flashcards

Constraints

Rules that enforce data integrity and ensure data consistency.

Signup and view all the flashcards

Modifying Table Structure

The process of changing a table's name, data types, or adding constraints.

Signup and view all the flashcards

UNIQUE

A keyword used to specify that a column is subject to the UNIQUE constraint.

Signup and view all the flashcards

ALTER TABLE ... ADD CONSTRAINT ... UNIQUE

A command in SQL used to add a UNIQUE constraint to an existing table.

Signup and view all the flashcards

Constraint Name (e.g., phone_unique)

A named identifier used to identify a UNIQUE constraint. It helps with organization and clarity.

Signup and view all the flashcards

Column Name

The column specified within the UNIQUE constraint to enforce uniqueness.

Signup and view all the flashcards

What is the INSERT command used for?

The INSERT command in SQL is used to add one or more new rows of data to a table.

Signup and view all the flashcards

What is the structure of the INSERT command?

The INTO keyword specifies the table you want to insert data into, and the column names you want to populate. The VALUES keyword specifies the values to be inserted for each column.

Signup and view all the flashcards

What is the correct syntax for the INSERT command?

The syntax for the INSERT command is:

INSERT INTO table_name (column1, column2, ...) VALUES (value1, value2, ...);

You specify the table name, column names, and corresponding values enclosed in parentheses.

Signup and view all the flashcards

Explain the example INSERT INTO person (ssn, fname, city, salary) VALUES ('234', 'Ali', 'Irbid', '450');

The example INSERT INTO person (ssn, fname, city, salary) VALUES ('234', 'Ali', 'Irbid', '450'); adds a new row to the person table with values '234' for ssn, 'Ali' for fname, 'Irbid' for city, and '450' for salary.

Signup and view all the flashcards

Why is the INSERT command important?

The INSERT command lets you add new data into your database tables. This allows you to update and expand your database as needed.

Signup and view all the flashcards

Study Notes

Database Design

  • Database design involves analysis, entity-relationship diagrams (ER diagrams), schema design (DDL), and data manipulation (DML).
  • Analysis is the initial step, defining entities (e.g., student, course) and their attributes (e.g., student ID, name, major).
  • Relationships between entities are specified (e.g., one-to-one, one-to-many, many-to-many relationships).
  • ER diagrams visually represent entities, attributes, and relationships.
  • Schema design (DDL) defines the structure of the database tables.
  • Data manipulation (DML) involves interacting with the data (e.g., inserting, updating, deleting).
  • Key attributes uniquely identify each entity. Examples include student ID, social security number, and serial numbers.

Attribute Types

  • Key Attribute: Uniquely identifies an entity, cannot duplicate (e.g., student ID).
  • Composite Attribute: Combination of single attributes (e.g., Address: city, street, etc.) to form complete information.
  • Multi-Value Attribute: Can have more than one value (e.g., phone numbers, email addresses).
  • Derived Attribute: Calculated from other attributes (e.g., age from birth date, GPA from grades).

Relationships

  • One-to-One (1:1): Each entity in one table corresponds to at most one entity in another table.
  • One-to-Many (1:M): One entity in one table can correspond to many entities in another table.
  • Many-to-Many (M:M): Many entities in one table can correspond to many entities in another table (often requiring an intermediary table).

Cardinality Ratio

  • Cardinality ratio describes the relationship between the entities: 1:1, 1:M, M:M.

Participation Constraint

  • Total Participation: Each entity in one table must be related to an entity in the other table.
  • Partial Participation: At least one entity in one table may not be related to an entity in the other table.

Types of Relationships

  • Binary Relationship: Two entities are involved in the relationship.
  • Recursive Relationship: A binary relationship where a relationship occurs within the same entity (e.g., employee is a supervisor of another employee).
  • Ternary Relationship: Three entities are involved.

Entity Types

  • Strong Entity: Exists independently and has its own key attribute.
  • Weak Entity: Dependent on a strong entity and does not have its own key attribute, needing a partial key from the strong entity to define it.

ER Diagram to Relational Schema Mapping

  • Entities in the ER diagram become tables in the relational schema.
  • Attributes become columns.
  • Relationships become relationships between tables using primary and foreign keys.

SQL

  • DDL (Data Definition Language) statements create, modify, and delete database objects (tables, columns, etc.).

    • Create, alter, drop table
    • Add, drop, alter columns

  • DML (Data Manipulation Language) statements manage data within database objects.

    • Insert, update, delete rows
    • Select, retrieve data

  • Constraints (e.g., NOT NULL, UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK) enforce data integrity and validity.

  • LIKE operator is used to filter data based on patterns (e.g., searching based on text patterns or names).

  • ORDER BY clause sorts the results of a query.

  • TOP clause limits the number of returned rows.

  • GROUP BY clause groups similar data to perform aggregate functions such as AVG, SUM, COUNT, and MAX.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Quiz Team

Related Documents

Database Design Notes PDF

More Like This

Use Quizgecko on...
Browser
Open
Browser
Browser