Introduction to SQL and Database Design
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Questions and Answers

What does SQL stand for?

Structured Query Language

Which of the following is NOT a common relational database management system that uses SQL?

  • Oracle
  • Sybase
  • Google Docs (correct)
  • Microsoft SQL Server

    • SQL is only used for relational database management systems.

    False

    Who is considered the "father of relational databases"?

    <p>Dr. Edgar F. &quot;Ted&quot; Codd</p> Signup and view all the answers

    What year did Structured Query Language appear?

    <p>1974</p> Signup and view all the answers

    What was the name of the product released by IBM in 1978 that developed Codd’s ideas?

    <p>System/R</p> Signup and view all the answers

    What does DDL stand for in SQL?

    <p>Data Definition Language</p> Signup and view all the answers

    What is the primary role of DML in SQL?

    <p>Data manipulation language</p> Signup and view all the answers

    What is the command used to create a new table in SQL?

    <p>CREATE TABLE</p> Signup and view all the answers

    What is the SQL command for selecting all data from a table called 'Account' where the 'Type' column equals "checking"?

    <p>SELECT * FROM Account WHERE Type = &quot;checking&quot;</p> Signup and view all the answers

    What is the SQL command used to grant access to a database?

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

    SQL DDL describes the specification about schema, domain, integrity constraints, security, and physical storage structure.

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

    The 'char(n)' data type in SQL allows for variable-length characters with user-specified maximum length n.

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

    'Numeric(p,d)' is a fixed-point number with user-specified precision. 'P' represents the total number of digits, and 'd' represents the number of digits to the right of the decimal point.

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

    Which data type is used for storing dates in SQL?

    <p>All of the above</p> Signup and view all the answers

    'Null' can only be used with 'date' data type.

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

    Write the SQL command to make a table called 'Account' with columns 'account number' as integer, 'branch name' as varchar(30) and 'balance' as integer, making 'account number' as the primary key.

    <p>CREATE TABLE Account (account_number INT PRIMARY KEY, branch_name VARCHAR(30), balance INT);</p> Signup and view all the answers

    What statement is used in SQL to declare a 'check' constraint?

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

    Which of the following is NOT an important constraint in SQL?

    <p>secondary key</p> Signup and view all the answers

    Write a SQL statement that demonstrates the 'foreign key (A1, ... ,An) references R' constraint to represent relationships between tables 'Customer' and 'Loan'. Consider fields 'customer_name' and 'loan_number' as keys in both tables.

    <p>CREATE TABLE Loan ( ... , customer_name VARCHAR(50), FOREIGN KEY (customer_name) REFERENCES Customer(customer_name));</p> Signup and view all the answers

    'CASCADE' constraint ensures that when rows in the master table are deleted, the corresponding rows in the child table are also deleted.

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

    What is the command in SQL to add a new attribute to an existing table?

    <p>ALTER TABLE ... ADD</p> Signup and view all the answers

    What command in SQL is used to rename an attribute in an existing table?

    <p>ALTER TABLE ... CHANGE</p> Signup and view all the answers

    What command in SQL is used to drop one or more attributes from an existing table?

    <p>ALTER TABLE ... DROP</p> Signup and view all the answers

    What is the SQL command to create a primary key constraint?

    <p>ALTER TABLE ... ADD PRIMARY KEY</p> Signup and view all the answers

    What is the SQL command to create a foreign key constraint?

    <p>ALTER TABLE ... ADD FOREIGN KEY</p> Signup and view all the answers

    When declaring an attribute in SQL, what keyword is used to set a default value?

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

    Indexes are visible to users.

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

    What are the key advantages of creating indexes in an SQL database?

    <p>Indexes dramatically improve search efficiency, allowing the database to retrieve data faster.</p> Signup and view all the answers

    Creating indexes on columns with a high number of NULL values is generally a good practice.

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

    Why is it not recommended to use indexes on small tables?

    <p>Indexes usually add overhead to data modification (insert, update, delete) operations. On small tables, this overhead is not worth the small performance improvement during searches.</p> Signup and view all the answers

    What are the 3 core SQL commands used for data modification within a database?

    <p>INSERT, DELETE, UPDATE</p> Signup and view all the answers

    The order of values in the INSERT statement matters.

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

    What SQL command is used to delete specific tuples (rows) from a table based on certain conditions?

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

    What is the command to update the balance of an account where the balance is greater than 1000 by multiplying it with 1.05?

    <p>UPDATE Account SET balance = balance * 1.05 WHERE balance &gt; 1000</p> Signup and view all the answers

    What is the purpose of a 'case' statement in SQL?

    <p>The 'CASE' statement allows you to evaluate different conditions and apply different actions based on the outcome. This creates conditional logic within SQL queries.</p> Signup and view all the answers

    Study Notes

    Introduction to SQL

    • SQL stands for Structured Query Language.
    • It's used to communicate with a database.
    • SQL is the standard language for relational database management systems (DBMS).
    • SQL statements are used to perform tasks like updating data and retrieving information from databases.
    • Many common relational database management systems use SQL, including Oracle, Sybase, Microsoft SQL Server, Access, and Ingres.

    Database Design Review

    • Database design involves several steps, including need analysis, data modeling (e.g., using Entity-Relationship diagrams), relational schema, and querying.
    • SQL is essential in interacting with databases following the design process.
    • DBMS + query is necessary for database design.

    SQL History

    • Dr. Edgar F. "Ted" Codd of IBM is considered the father of relational databases.
    • He developed the relational model for databases.
    • Structured Query Language (SQL) emerged in the 1970s.
    • IBM developed System/R in the 1978, furthering Codd's ideas.
    • IBM created the first prototype of the relational database and standardized it with ANSI in 1986; Relational Software later became known as Oracle.

    SQL Parts

    • DDL (Data Definition Language): Used for creating tables and views, forming the database's foundation.
    • DML (Data Manipulation Language): Manages data within the database, including performing queries and updates.
    • DCL (Data Control Language): Governs access control to data in the database (e.g., providing authorization).

    SQL Illustration

    • DDL: Foundation/Structure of the database
    • DML: Contents within the database
    • DCL: Access to the database

    Sample SQL Parts

    • DDL Example: Creating a table named Account that has attributes for AccNumber, Owner, Balance,AccType and creating a PRIMARY KEY for Number.
    • DML Example: Selecting data from the Account table where Type equals "checking".
    • DCL Example: Granting all permissions on the database banking to teller with password password.

    Data Definition Language (DDL)

    • SQL DDL specifies details about the database, including:
      • Schema for each relation
      • Domain of each attribute
      • Integrity constraints
      • Index-set maintained for each relation
      • Security and authorization information
      • Physical storage structure of each relation on disk

    Basic Domain Types

    • char(n): Fixed-length character string
    • varchar(n): Variable-length character string
    • int, mediumint, smallint, tinyint: Integer types
    • numeric(p,d): Fixed-point number
    • real, double precision: Floating-point numbers
    • float(n): Floating-point number with precision at least n digits
    • date: Date-time values
    • time: Time-only values
    • timestamp: Combined date and time
    • null: Absence of a value

    Relation Schema Sample

    • branch: Holds branch information
    • customer: Holds customer details
    • loan: Stores loan information
    • borrower: Links customers to loans
    • account: Represents account details
    • depositor: Associates customers with accounts

    Creating Table Command

    • create table r (A₁ D1, A2 D2, ..., An Dn, ...): General form
      • r is the table name
      • Aᵢ is a field in the table
      • Dᵢ is the data type for field Aᵢ
    • Constraints like primary key and not null can be applied.
    • Example- creating a branch table.

    Integrity Constraints in Creating Table

    • not null: Specifies that a column cannot hold NULL values.
    • primary key (A₁, ..., An): Uniquely identifies each row in a table.
    • check(P): Ensures that all rows in a table must satisfy the condition P. Integrity constraint
    • foreign key: Establishes a relationship between two tables.

    Cascade

    • Used in relationships
    • Operations on one table (master) can trigger related actions in another table (child).
    • Rows get deleted or updated due to an event in the Master table.

    Alter Table Commands

    • Modifies existing tables by adding, deleting, or updating columns, primary keys or other constraints.

    Default Values

    • Provides default values to attributes.
    • Makes data input less tedious.
    • DEFAULT keyword followed by NULL or a fixed value.

    Indexes

    • Indexes are special lookup tables that the database search engine can use to speed up data retrieval.
    • Users don't see indexes.
    • Indexes are used to quickly locate data. They are created on columns that are frequently searched against.

    Data Manipulation Language (CRUD)

    • CRUD: Create, Read, Update and Delete
    • Basic data modifications in database, including adding, deleting, and modifying data.

    Insertion

    • INSERT INTO R(A₁, ...,An) VALUES (v₁, ...,vn):Adds a new tuple to a table.

    Deletion

    • Removes from a table by specifying a WHERE clause.

    Updates

    • Modifies existing data in a table, changing column values.
    • update R set attribute = expression where <condition> is the basic form.
    • Example: Adjusting account balances based on specific conditions.

    Case Statements

    • Used for conditional logic in SQL updates
    • Allow for diverse modifications in database entries.

    Conclusion

    • This overview covers fundamental aspects of SQL. It's crucial for interacting with and managing databases effectively.

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    Related Documents

    SQL Data Definition Language (DDL) PDF

    Description

    This quiz covers the basics of Structured Query Language (SQL), its role in relational database management systems (DBMS), and key concepts in database design. Additionally, it touches on the historical foundation of SQL and its development over the years. Test your knowledge on these essential database principles!

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