Question
Which of the following has the shortest
wavelength?Solution
Gamma rays have the shortest wavelength and radio waves have the longest wavelength. An electromagnetic wave with wavelengths from 0.01 nm to 10 nm called X-rays. Decreasing order of the wavelength: Radio waves > Ultraviolet > X-rays > Gamma rays
A star schema in a data warehouse consists of:
A snowflake schema differs from a star schema mainly because:
Which of the following is used to maintain information about the structure of a data warehouse?
In a data warehouse, which type of table stores quantitative data for analysis?
What is the result of SELECT COALESCE(NULL, NULL, 5, 10);?
Which OLAP operation involves focusing on a subset of dimensions (e.g., region=‘Asia’)?
Which SQL query will correctly calculate the average salary of employees in each department and group them by department in a table named 'employees'?
Which SQL function returns the total number of rows in a table?
Which SQL keyword is used to combine results from two queries and remove duplicates?
What is a data mart?
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