Unit 2

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Questions and Answers

What is a key advantage of SQLite's portability?

It can only operate on Windows systems.

It can run on both 32-bit and 64-bit architectures. (correct)

It requires specific programming languages to function.

It is designed for high traffic HTTP requests.

Which statement accurately describes SQLite's access capabilities?

It allows multiple processes to interact without interference. (correct)

It can only be accessed by a single user at a time.

The database's content is less likely to be recoverable once lost.

It is not compatible with third-party tools.

What does SQLite do to reduce costs and complexity in applications?

It uses lengthy procedural queries.

It allows concise SQL queries for data access. (correct)

It requires complex system configurations.

It mandates expensive hardware upgrades.

What is one main limitation of SQLite?

The maximum database size is generally limited to 2GB. Signup and view all the answers

Which of the following is a step in installing SQLite on Windows 7?

Download a specific version of sqlite-tools. Signup and view all the answers

What feature is NOT supported by SQLite according to SQL92?

RIGHT OUTER JOIN Signup and view all the answers

What should you do after extracting the SQLite zip file?

Create a folder named 'sqlite3' in C:/. Signup and view all the answers

Which step verifies that the path for sqlite3.exe is set correctly?

Writing 'Sqlite3' in the Command Prompt. Signup and view all the answers

What is the primary purpose of the DISTINCT operator in SQLite?

To remove duplicate records from the results Signup and view all the answers

How does the BETWEEN operator function in an SQL query?

It retrieves records within a specified range Signup and view all the answers

Which of the following SQL statements correctly uses the IN operator?

SELECT * FROM table_name WHERE column_name IN (value1, value2) Signup and view all the answers

What does the UNION operator achieve in an SQL statement?

It combines results from two or more queries and removes duplicates Signup and view all the answers

What is required for all SELECT statements when using the UNION operator?

Each SELECT must use the same number of columns Signup and view all the answers

What does the condition 'Where FEES like '_00%'` check for?

Values that have 00 in the second and third positions Signup and view all the answers

What is the purpose of the LIMIT clause in a SELECT statement?

To specify the number of rows returned Signup and view all the answers

What would the query 'SELECT * FROM EMPLOYEE WHERE EMP_ID NOT BETWEEN 102 AND 105;' return?

Records with EMP_IDs either lower than 102 or higher than 105 Signup and view all the answers

Which SQL command will retrieve a list of all unique values in 'column1' from 'table1'?

SELECT DISTINCT column1 FROM table1 Signup and view all the answers

How can you skip a certain number of rows in a query result?

By combining LIMIT and OFFSET clauses Signup and view all the answers

What does the HAVING clause do in a SQL query?

Specifies conditions on groups created by the GROUP BY clause Signup and view all the answers

What result does the INTERSECT operator provide in an SQL context?

It returns only the common records from two or more tables Signup and view all the answers

In an ORDER BY clause, which of the following is true?

All columns used in ORDER BY must be in column-list Signup and view all the answers

What does the statement 'Where FEES like '2_%_%'' do?

Finds any values starting with 2 Signup and view all the answers

Which statement accurately describes the GROUP BY clause?

It organizes identical elements into distinct groups Signup and view all the answers

What result does the pattern 'Where FEES like '%2'' provide?

Finds values that end with the digit 2 Signup and view all the answers

Which commands are included in the Data Definition Language (DDL) of SQLite?

CREATE, ALTER, DROP Signup and view all the answers

What type of trigger does SQLite support?

FOR EACH ROW triggers Signup and view all the answers

Which of the following statements about SQLite views is true?

Views are read-only in SQLite. Signup and view all the answers

What modifications can be made using the ALTER TABLE command in SQLite?

Add a column and rename a table Signup and view all the answers

Which permission types can be granted or revoked in SQLite?

Normal file access permissions of the operating system Signup and view all the answers

What differentiates a Full Outer Join from a LEFT OUTER JOIN in SQLite?

Only LEFT OUTER JOIN is implemented. Signup and view all the answers

Which command is used to delete records from a table in SQLite?

DELETE Signup and view all the answers

What does the SQLite dot command '.help' do?

Show the help menu Signup and view all the answers

What effect does the COMMIT command have in a transaction?

It permanently applies all changes made during the transaction. Signup and view all the answers

When would you use the ROLLBACK command?

To cancel changes made since the last COMMIT or ROLLBACK. Signup and view all the answers

What is a savepoint in SQLite transactions?

A marker that allows for rolling back to a specific point in a transaction. Signup and view all the answers

Which command would you use to release a savepoint in SQLite?

RELEASE Signup and view all the answers

What happens when the ROLLBACK command is executed after a transaction that has not yet been committed?

All changes made in the current transaction are undone. Signup and view all the answers

If a transaction is begun and a DELETE command is executed, which command must be used to confirm the changes permanently?

COMMIT Signup and view all the answers

How can multiple savepoints be used within a single transaction?

Each savepoint must have a unique name. Signup and view all the answers

What will happen if you try to execute a ROLLBACK command after a COMMIT command has been issued?

It will do nothing as the changes are already permanent. Signup and view all the answers

Study Notes

SQLite Overview

SQLite is portable, functioning across all 32-bit and 64-bit operating systems, supporting both big- and little-endian architectures.
Multiple processes can connect to the same SQLite file, allowing concurrency without conflicts.
Compatible with all programming languages, simplifying integration without compatibility issues.

Accessibility

Wide accessibility through various third-party tools for managing SQLite databases.
Data recovery is more feasible due to its design principles; data remains accessible longer than code.

Cost and Complexity Reduction

Reduces overall application costs by enabling concise SQL queries, minimizing lengthy procedural code.
Future enhancements can be implemented easily by adding new tables or columns without extensive rewrites.

Disadvantages of SQLite

Suitable for handling low to medium traffic HTTP requests but may struggle under high loads.
Database size limit typically set to 2GB, impacting scalability.

Installation Steps for SQLite on Windows 7

Visit the official SQLite website to download the appropriate version based on system architecture.
Extract files and set up a dedicated folder in the C: directory for SQLite components.
Configure the system's environment variables to include the SQLite executable path for easy access.
Verify installation through the Command Prompt by invoking sqlite3.

SQL92 Features Not Supported

Only LEFT OUTER JOIN is supported; RIGHT and FULL OUTER JOIN are not implemented.
ALTER TABLE lacks support for DROP COLUMN, ALTER COLUMN, and ADD CONSTRAINT commands.
Triggers are limited to FOR EACH ROW; triggers for EACH STATEMENT are not supported.
Views are read-only with no capability for DELETE, INSERT, or UPDATE operations.
Access permissions are limited to those offered by the operating system's file-level permissions.

SQLite Command Types

Three primary command types:
- DDL (Data Definition Language) includes CREATE, ALTER, DROP for structure management.
- DML (Data Manipulation Language) covers INSERT, UPDATE, DELETE for data handling.
- DQL (Data Query Language) includes SELECT to retrieve data.

SQLite Dot Commands

.help provides assistance with commands.
.show displays current settings and their values.
.exit or .quit terminates the SQLite prompt.

Querying Data with Various Clauses

LIMIT clause restricts the number of rows returned by a SELECT statement, optionally combined with OFFSET for paging results.
ORDER BY arranges results based on specified columns; multiple columns can be sorted.
GROUP BY aggregates records into groups, often with HAVING to filter those groups.
DISTINCT operator retrieves unique records, eliminating duplicates from results.
IN operator allows comparison against a defined list of values.
BETWEEN operator fetches records within a specified range.

Combining Results

UNION operator merges result sets from multiple SELECT statements while excluding duplicates.
INTERSECT operator returns only common records present in multiple result sets.

Transaction Control in SQLite

ROLLBACK command undoes changes made in a transaction since the last COMMIT or ROLLBACK.
COMMIT command saves all changes within the transaction to the database.
The SAVEPOINT command enables the creation of nested transactions, allowing selective rollback or commit to specific stages within a transaction.

Example Use Case for ROLLBACK

A transaction can be initiated to delete certain records; using ROLLBACK will retain the original data while committing changes would finalize the deletions.

SQLite Savepoint Usage

Savepoints are markers within transactions to facilitate partial rollbacks, enhancing control over changes.
RELEASE command accepts changes made from a specific savepoint, leaving other operations intact.

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Description

This quiz covers the key features of SQLite, including its portability across different operating systems and architectures. It also explores accessibility and compatibility with various programming languages. Test your knowledge on how SQLite can be utilized in Python applications.