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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?
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?
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?
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?
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?
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;?
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?
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?
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?
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?
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?
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?
What is the primary purpose of a 'cell' in a relational database?
In the context of relational databases, what constitutes an 'empty table'?
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?
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?
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?
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?
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?
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?
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?
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
Integer
Represents whole numbers. Storage size varies (1, 2, 3, 4, or 8 bytes) depending on range.
Decimal
Decimal
Represents exact decimal numbers. Storage varies based on precision.
Float
Float
Represents approximate decimal numbers, using 4 bytes of storage.
Double
Double
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Date
Date
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Time
Time
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Datetime
Datetime
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Char(N)
Char(N)
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Varchar(N)
Varchar(N)
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Text
Text
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ALTER TABLE ADD
ALTER TABLE ADD
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ALTER TABLE CHANGE
ALTER TABLE CHANGE
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ALTER TABLE DROP
ALTER TABLE DROP
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CREATE TABLE
CREATE TABLE
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DROP TABLE
DROP TABLE
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SHOW DATABASES
SHOW DATABASES
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SHOW TABLES FROM databaseName
SHOW TABLES FROM databaseName
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USE databaseName
USE databaseName
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SHOW COLUMNS FROM TableName
SHOW COLUMNS FROM TableName
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Cell
Cell
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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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