d492 Data Analytics Applications - Set 2 - Part 1

Correct Answer: INSERT

The INSERT command is used to add a new row to a table. UPDATE modifies existing rows, SELECT retrieves data, and DELETE removes rows from a table.

Correct Answer: JOIN

The JOIN operation combines two tables by matching rows based on related columns. UNION combines all rows of two tables, PROJECT selects specific columns, and RENAME changes the name of a table or column.

Correct Answer: WHERE

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

Correct Answer: Both a and c

A FOREIGN KEY links two tables together and ensures referential integrity by enforcing that the value in one table corresponds to a valid value in another table. It does not uniquely identify rows, which is the role of the PRIMARY KEY.

Correct Answer: UNION

The UNION keyword combines all rows from two tables into a single result set, removing duplicates. INTERSECT selects only the rows that are common between two tables, JOIN combines rows based on a relationship, and PRODUCT produces all combinations of rows from two tables.

Correct Answer: GROUP BY

The GROUP BY clause groups rows that have the same values in specified columns. It is often used with aggregate functions to provide summary data. WHERE filters rows, HAVING filters groups, and ORDER BY sorts the result set.

Correct Answer: ALTER

The ALTER command modifies the structure of an existing table, such as adding or deleting columns. INSERT adds rows, CREATE creates new tables, and DROP removes tables or databases.

Correct Answer: SELECT

The SELECT operation in relational algebra is used to choose rows that meet a specified condition. PROJECT chooses columns, JOIN combines tables, and UNION combines rows from two tables.

Correct Answer: Removes duplicate rows from the result set

The DISTINCT keyword eliminates duplicate rows from the result set. WHERE filters rows, JOIN combines rows from multiple tables, and ORDER BY sorts the result set.

Correct Answer: AGGREGATE

The AGGREGATE operation computes functions over multiple rows, such as SUM(), COUNT(), and AVG(). UNION merges two tables, JOIN combines rows, and PRODUCT lists all combinations of rows from two tables.

Correct Answer: ABS()

The ABS() function returns the absolute value of a number. ROUND() rounds a number to a specified number of decimal places, POW() raises a number to a power, and SQRT() returns the square root.

Correct Answer: ORDER BY

The ORDER BY clause is used to sort the results of a query in ascending or descending order. WHERE filters rows, GROUP BY groups rows, and HAVING filters groups.

Correct Answer: To uniquely identify each row in a table

The PRIMARY KEY uniquely identifies each row in a table and ensures that no duplicate values exist. It does not link tables or store binary data.

Correct Answer: LIKE

The LIKE operator is used in SQL to search for a specified pattern in a column, often using wildcards like %. BETWEEN is used for range conditions, IN checks if a value is in a list, and EXISTS checks for the existence of rows in a subquery.

Correct Answer: To combine rows from two or more tables

The JOIN operation combines rows from two or more tables based on a related column. It is not used to insert, remove, or filter rows.

Correct Answer: SQRT()

The SQRT() function returns the square root of a number. ROUND() rounds a number, POW() raises a number to a power, and ABS() returns the absolute value.

Correct Answer: TRUNCATE

The TRUNCATE command removes all rows from a table but keeps the table structure intact. DELETE can remove specific rows, DROP removes the entire table, and ALTER modifies the structure of a table.

Correct Answer: Selects rows that are common to two tables

The INTERSECT operator selects rows that are common between two tables. UNION combines all rows, DISTINCT removes duplicates, and UNION ALL combines rows without removing duplicates.

Correct Answer: Foreign Key

A Foreign Key refers to the primary key in another table and creates a relationship between the two tables. A Primary Key uniquely identifies rows, a Candidate Key is a potential primary key, and a Unique Key enforces uniqueness but does not reference another table.

Correct Answer: To filter groups after aggregation

The HAVING clause is used to filter groups after they have been aggregated, typically used with GROUP BY. WHERE filters rows before aggregation, and ORDER BY sorts the result set.