Database Data Types

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Questions and Answers

When defining a column to store the number of products in an inventory system, which integer data type would be most appropriate if you anticipate needing to store values up to 50,000 but want to minimize storage space?

TINYINT
MEDIUMINT
SMALLINT (correct)
INTEGER

A database needs to store product prices. The prices must be accurate to two decimal places, and the highest expected price is $999.99. Which data type is most suitable?

DECIMAL(5, 2) (correct)
INTEGER
DOUBLE
FLOAT

For a column designed to track the exact time when a user last accessed their account, which data type is the most efficient and appropriate?

DATETIME (correct)
TIME
VARCHAR
DATE

If a database column needs to store customer names, and you know that most names will be less than 30 characters, but some could be as long as 50 characters, what is the most appropriate data type to use to balance storage efficiency and accommodate all names?

VARCHAR(50) (D)

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You have a `Student` table with columns `ID`, `FirstName`, `LastName`, and `GPA`. Which SQL statement will fail because of a syntax error?

<code>SELECT GPA FORM Student;</code> (B)

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What is the error in the SQL statement `SELECT FirstName FROM Student WHERE LastName = Smith;`?

The literal <code>Smith</code> must be enclosed in quotes. (D)

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Consider inserting a new record into the `Student` table with the statement `INSERT INTO Student VALUES (101, 'John', 'Doe', 3.5);`. How many clauses are implicitly used in this simplified `INSERT` statement?

2 (D)

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Which SQL command lists all available databases in the current database system?

SHOW DATABASES; (B)

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To view all tables within the `EmployeeDB` database, which sequence of SQL statements should you execute?

<code>USE EmployeeDB; SHOW TABLES;</code> (C)

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Before using `SHOW TABLES` to list tables in the `SalesDB` database, which command is essential to specify the database context?

<code>USE SalesDB;</code> (B)

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To inspect the structure of the `Customers` table, specifically to see all its columns, which SQL statement should be used?

<code>SHOW COLUMNS FROM Customers;</code> (B)

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What is the primary purpose of a 'cell' in a relational database?

To represent a single value at the intersection of a row and a column. (B)

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In the context of relational databases, what constitutes an 'empty table'?

A table with no rows. (C)

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Which `ALTER TABLE` clause is used to introduce a new field named `Email` with a `VARCHAR(100)` data type to an existing table named `Users`?

<code>ALTER TABLE Users ADD Email VARCHAR(100);</code> (A)

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To rename a column from `ContactNumber` to `PhoneNumber` in the `Customers` table, which `ALTER TABLE` command should you use?

<code>ALTER TABLE Customers CHANGE ContactNumber PhoneNumber INT;</code> (B)

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Which `ALTER TABLE` clause removes the `Address` column from the `Clients` table?

<code>ALTER TABLE Clients DROP COLUMN Address;</code> (A)

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When creating a table to store dates of historical events, which data type is most suitable for the column that will hold the event dates?

DATE (A)

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In a database maintaining financial records, which data type is ideal for storing monetary values that require precise calculations without rounding errors?

DECIMAL (D)

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What is the effect of executing a `DROP TABLE` statement on a table in a relational database?

It deletes the table and all its data from the database. (D)

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You need to create a `Products` table with columns for `ProductID` (integer), `ProductName` (variable-length string), and `Price` (accurate to two decimal places). Which set of data types is most appropriate?

<code>ProductID INT, ProductName VARCHAR, Price DECIMAL(10, 2)</code> (C)

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Flashcards

Integer

Represents whole numbers. Storage size varies (1, 2, 3, 4, or 8 bytes) depending on range.

Decimal

Represents exact decimal numbers. Storage varies based on precision.

Float

Represents approximate decimal numbers, using 4 bytes of storage.

Double

Represents approximate decimal numbers with higher precision, using 8 bytes.

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Date

Stores date values in 'YYYY-MM-DD' format, using 3 bytes.

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Time

Stores time values in 'hh:mm:ss' format, using 3 bytes.

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Datetime

Stores both date and time values in 'YYYY-MM-DD hh:mm:ss' format, using 5 bytes.

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Char(N)

Fixed-length string of length N, using N bytes of storage.

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Varchar(N)

Variable-length string with maximum N characters. Storage is length + 1 bytes.

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Text

Variable-length string with a maximum of 65,535 characters. Storage is length + 2 bytes.

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ALTER TABLE ADD

Adds a new column to an existing table.

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ALTER TABLE CHANGE

Modifies the name or data type of an existing column.

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ALTER TABLE DROP

Removes a column from a table.

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CREATE TABLE

Creates a new table with specified columns and data types.

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DROP TABLE

Deletes a table and its data from the database.

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SHOW DATABASES

Displays all databases available in the database system.

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SHOW TABLES FROM databaseName

Displays all tables within the specified database.

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USE databaseName

Specifies the database to be used for subsequent operations.

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SHOW COLUMNS FROM TableName

Displays the column definitions for the specified table.

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Cell

A single piece of data at the intersection of a row and a column.

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Study Notes

Data Types

Integer:
- TINYINT: 1 byte, Signed range: -128 to 127, Unsigned range: 0 to 255.
- SMALLINT: 2 bytes, Signed range: -32,768 to 32,767, Unsigned range: 0 to 65,535.
- MEDIUMINT: 3 bytes, Signed range: -8,388,608 to 8,388,607, Unsigned range: 0 to 16,777,215.
- INTEGER or INT: 4 bytes, Signed range: -2,147,483,648 to 2,147,483,647, Unsigned range: 0 to 4,294,967,295.
- BIGINT: 8 bytes, Signed range: -2^63 to 2^63 - 1, Unsigned range: 0 to 2^64 - 1.
Decimal:
- DECIMAL(M,D): Varies in storage, exact decimal number, M = total significant digits, D = digits after decimal.
Floating Point:
- FLOAT: 4 bytes, approximate decimal, range: -3.4E+38 to 3.4E+38.
- DOUBLE: 8 bytes, approximate decimal, range: -1.8E+308 to 1.8E+308.
Date and Time:
- DATE: 3 bytes, format YYYY-MM-DD, range '1000-01-01' to '9999-12-31'.
- TIME: 3 bytes, format hh:mm:ss.
- DATETIME: 5 bytes, format YYYY-MM-DD hh:mm:ss, range '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.
Character:
- CHAR(N): N bytes, fixed-length string, length N, 0 ≤ N ≤ 255.
- VARCHAR(N): Length of characters + 1 byte, variable-length string, maximum N characters, 0 ≤ N ≤ 65,535.
- TEXT: Length of characters + 2 bytes, variable-length string, maximum 65,535 characters.

SQL Errors and Statements

A literal string in a WHERE clause requires single or double quotes.
The FROM keyword must be written as FROM
INSERT statements add data to tables.
SHOW DATABASES displays all databases in a database system.
SHOW TABLES displays all tables in a database.
USE databaseName must precede SHOW TABLES to specify the database.
SHOW COLUMNS FROM TableName displays columns in a table.

Relational Databases Structure

Data in relational databases is structured in tables with a name, fixed columns, and varying rows.
Columns have a name and a data type.
Rows are sequences of values corresponding to column data types, forming cells at intersections.
Tables require at least one column and can have any number of rows, with empty tables allowed.

ALTER TABLE Statement

ADD: Adds a column: ALTER TABLE TableName ADD ColumnName DataType;
CHANGE: Modifies a column: ALTER TABLE TableName CHANGE CurrentColumnName NewColumnName NewDataType;
DROP: Deletes a column: ALTER TABLE TableName DROP ColumnName;

CREATE TABLE and DROP TABLE Statements

CREATE TABLE: Creates a new table with specified name, column names, and data types.
- INT or INTEGER: Integer values.
- VARCHAR(N): Values with 0 to N characters.
- DATE: Date values.
- DECIMAL(M, D): Numeric values with M total digits and D digits after the decimal point.
DROP TABLE: Deletes a table and all its rows from a database.

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Questions and Answers

When defining a column to store the number of products in an inventory system, which integer data type would be most appropriate if you anticipate needing to store values up to 50,000 but want to minimize storage space?

A database needs to store product prices. The prices must be accurate to two decimal places, and the highest expected price is $999.99. Which data type is most suitable?

For a column designed to track the exact time when a user last accessed their account, which data type is the most efficient and appropriate?

If a database column needs to store customer names, and you know that most names will be less than 30 characters, but some could be as long as 50 characters, what is the most appropriate data type to use to balance storage efficiency and accommodate all names?

You have a Student table with columns ID, FirstName, LastName, and GPA. Which SQL statement will fail because of a syntax error?

What is the error in the SQL statement SELECT FirstName FROM Student WHERE LastName = Smith;?

Consider inserting a new record into the Student table with the statement INSERT INTO Student VALUES (101, 'John', 'Doe', 3.5);. How many clauses are implicitly used in this simplified INSERT statement?

Which SQL command lists all available databases in the current database system?

To view all tables within the EmployeeDB database, which sequence of SQL statements should you execute?

Before using SHOW TABLES to list tables in the SalesDB database, which command is essential to specify the database context?

To inspect the structure of the Customers table, specifically to see all its columns, which SQL statement should be used?

What is the primary purpose of a 'cell' in a relational database?

In the context of relational databases, what constitutes an 'empty table'?

Which ALTER TABLE clause is used to introduce a new field named Email with a VARCHAR(100) data type to an existing table named Users?

To rename a column from ContactNumber to PhoneNumber in the Customers table, which ALTER TABLE command should you use?

Which ALTER TABLE clause removes the Address column from the Clients table?

When creating a table to store dates of historical events, which data type is most suitable for the column that will hold the event dates?

In a database maintaining financial records, which data type is ideal for storing monetary values that require precise calculations without rounding errors?

What is the effect of executing a DROP TABLE statement on a table in a relational database?

You need to create a Products table with columns for ProductID (integer), ProductName (variable-length string), and Price (accurate to two decimal places). Which set of data types is most appropriate?

Flashcards

Integer

Decimal

Float

Double

Date

Time

Datetime

Char(N)

Varchar(N)

Text

ALTER TABLE ADD

ALTER TABLE CHANGE

ALTER TABLE DROP

CREATE TABLE

DROP TABLE

SHOW DATABASES

SHOW TABLES FROM databaseName

USE databaseName

SHOW COLUMNS FROM TableName

Cell

Study Notes

Data Types

SQL Errors and Statements

Relational Databases Structure

ALTER TABLE Statement

CREATE TABLE and DROP TABLE Statements

Studying That Suits You

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You have a `Student` table with columns `ID`, `FirstName`, `LastName`, and `GPA`. Which SQL statement will fail because of a syntax error?

What is the error in the SQL statement `SELECT FirstName FROM Student WHERE LastName = Smith;`?

Consider inserting a new record into the `Student` table with the statement `INSERT INTO Student VALUES (101, 'John', 'Doe', 3.5);`. How many clauses are implicitly used in this simplified `INSERT` statement?

To view all tables within the `EmployeeDB` database, which sequence of SQL statements should you execute?

Before using `SHOW TABLES` to list tables in the `SalesDB` database, which command is essential to specify the database context?

To inspect the structure of the `Customers` table, specifically to see all its columns, which SQL statement should be used?

Which `ALTER TABLE` clause is used to introduce a new field named `Email` with a `VARCHAR(100)` data type to an existing table named `Users`?

To rename a column from `ContactNumber` to `PhoneNumber` in the `Customers` table, which `ALTER TABLE` command should you use?

Which `ALTER TABLE` clause removes the `Address` column from the `Clients` table?

What is the effect of executing a `DROP TABLE` statement on a table in a relational database?

You need to create a `Products` table with columns for `ProductID` (integer), `ProductName` (variable-length string), and `Price` (accurate to two decimal places). Which set of data types is most appropriate?