Cell membranes can maintain a difference in electrical charg…
Cell membranes can maintain a difference in electrical charge between the inte- rior of the cell and the extracellular fluid. What is this charge difference called? A. excitabilityB. the membrane potentialC. the action potentialD. the sodium-potassium pump
Read DetailsA retail company wants to calculate the change in daily sale…
A retail company wants to calculate the change in daily sales compared to the prior day. Which window function concept is most directly applied here? OPTIONS:A. Aggregating data with GROUP BYB. Accessing the previous row using LAGC. Accessing the next row using LEADD. Filtering data with WHERE ANSWER:B EXPLANATION:LAG retrieves the previous row’s value, which allows day-over-day comparisons.
Read DetailsAn e-commerce analyst wants to compare each day’s sales to t…
An e-commerce analyst wants to compare each day’s sales to the previous day’s sales in order to spot drops in performance. Which SQL window function is best suited for this? OPTIONS:A. SUM OVER (PARTITION BY day)B. LAG with ORDER BY sale_dateC. LEAD with ORDER BY sale_dateD. ROW_NUMBER with PARTITION BY sale_date ANSWER:B EXPLANATION:LAG allows access to the previous row’s value when ordered by date, which is exactly what the analyst needs. LEAD looks forward (C), SUM aggregates without comparing rows (A), and ROW_NUMBER just assigns sequence numbers (D).
Read DetailsA recruiter wants to assign each applicant a unique number i…
A recruiter wants to assign each applicant a unique number in order of application date: SELECT applicant_id, application_date, ROW_NUMBER() OVER (ORDER BY application_date) AS row_num FROM applicants; What does the row_num column show? OPTIONS:A. A sequential number for each applicant, ordered by application dateB. The count of applicants who applied on the same dayC. The average application date per applicantD. The difference in days between applications ANSWER:A EXPLANATION:ROW_NUMBER() generates a sequential number based on the specified ordering, with no ties allowed.
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