d492 Data Analytics Applications - Set 1 - Part 1

Correct Answer: SELECT

The SELECT clause is used in SQL to query and retrieve data from a database table. INSERT adds new rows, DELETE removes rows, and UPDATE modifies existing rows.

Correct Answer: An ordered collection of elements

In a relational database, a tuple represents a single row in a table and is an ordered collection of elements. Unordered collections are sets, key-value pairs are used in NoSQL databases, and relationships between tables are managed through keys.

Correct Answer: DROP

The DROP command is used to completely remove a table from the database. DELETE removes rows from a table, TRUNCATE clears all rows but keeps the table structure, and ALTER modifies the structure of a table.

Correct Answer: PROJECT

The PROJECT operation is used to select specific columns of a table, eliminating the others. SELECT retrieves rows, JOIN combines tables based on a condition, and UNION merges two tables into one.

Correct Answer: AS

The AS keyword is used to rename columns or tables in SQL query results. FROM specifies the table, RENAME is not used in query results, and ALIAS is a general term for renaming but not a keyword.

Correct Answer: Groups rows that have the same values in specified columns

The GROUP BY clause groups rows that share values in specified columns, often used with aggregate functions. ORDER BY sorts the result set, WHERE filters rows, and DISTINCT removes duplicates.

Correct Answer: PRODUCT

The PRODUCT operation in relational algebra combines all rows from two tables. SELECT and PROJECT are unary operations, while RENAME changes table or column names.

Correct Answer: WHERE

The WHERE clause is used to filter records based on a specified condition. SELECT retrieves data, GROUP BY groups rows, and ORDER BY sorts the result set.

Correct Answer: A column that contains unique values for each row

A primary key uniquely identifies each row in a table. It cannot contain duplicate values, while foreign keys refer to other tables, and binary data is not related to primary keys.

Correct Answer: CREATE TABLE

The CREATE TABLE command is used to create a new table in a database. CREATE DATABASE creates a new database, ALTER TABLE modifies an existing table, and INSERT INTO adds data to a table.

Correct Answer: COUNT()

The COUNT() function returns the number of rows in a table. SUM() adds numeric values, AVG() calculates the average, and MAX() returns the maximum value.

Correct Answer: Links rows from two tables based on a related column

A foreign key links rows in two tables by referencing a primary key in another table. A primary key uniquely identifies rows, while binary data and temporary tables are unrelated to foreign keys.

Correct Answer: UPDATE

The UPDATE statement is used to modify existing data in a row. INSERT adds new rows, DELETE removes rows, and SELECT retrieves data without modification.

Correct Answer: Filters rows based on aggregate functions

The HAVING clause filters rows after aggregation, commonly used with GROUP BY. WHERE filters rows before aggregation, and ORDER BY sorts rows. DISTINCT removes duplicate rows.

Correct Answer: RAM

RAM is volatile memory, meaning its data is lost when power is turned off. Hard drives, flash memory, and magnetic tapes are non-volatile, retaining data without power.

Correct Answer: The process of organizing data to reduce redundancy

Normalization organizes data in a way that reduces redundancy and ensures data integrity. It is unrelated to query speed, storage capacity, or data filtering.

Correct Answer: A sequence of one or more SQL operations treated as a single unit

A transaction in a database is a sequence of operations performed as a single logical unit. Transactions ensure data integrity and consistency. Queries and filtering are individual operations, while query optimization is unrelated.

Correct Answer: COUNT()

COUNT() is an aggregate function that returns the number of rows in a result set. IFNULL() handles null values, CONCAT() concatenates strings, and SUBSTRING() extracts a portion of a string.

Correct Answer: Combines rows from two or more tables based on a related column

The JOIN clause combines rows from different tables based on a related column. It does not delete rows, rename columns or tables, or group rows.

Correct Answer: INNER JOIN

An INNER JOIN returns only rows that have matching values in both tables. LEFT JOIN returns all rows from the left table, RIGHT JOIN returns all rows from the right table, and FULL JOIN returns all rows from both tables.