Question at position 31 Which of the following is a valid window function?COUNT()ROW_NUMBER()SUM()All of these单项选择题
A
COUNT()
B
ROW_NUMBER()
C
SUM()
D
All of these

Question

Question at position 31 Which of the following is a valid window function?COUNT()ROW_NUMBER()SUM()All of these

BlackTom AI · Accepted Answer

To tackle the question, I’ll evaluate each option in turn and explain what window functions are used for in SQL contexts.
Option 1: 'COUNT()' — While COUNT() is often used as an aggregate function, it can also be used as a window function when combined with OVER(...) to count rows within a specified partition or frame. This makes COUNT() valid in a window-function context.
Option 2: 'ROW_NUMBER()' — ROW_NUMBER() is a canonical example of a window function. It assigns a unique sequential number to rows within a partition, ordered by a given ORDER BY clause inside OVER(...). There’s no ambiguity about its status as a window function.
Option 3: 'SUM()' — Similar to COUNT(), SUM() is typically an aggregate function, but it also becomes a window function when used with OVER(...). It can compute running totals or partitioned sums within windows, which is a standard window-function use.
Option 4: 'All of these' — Since COUNT(), ROW_NUMBER(), and SUM() can each function as window functions when paired with OVER(...), the statement that all of these are valid window functions is correct. Misconceptions often arise from confusing their aggregate usage without OVER(...) with their window-function capability, but the presence of OVER(...) changes their role from pure aggregation to windowed computation.
In summary, the question hinges on recognizing that each of the listed functions can act as a window function in SQL when used with the OVER() clause, so the most comprehensive and accurate choice is that all of them are valid window functions.

Question at position 31 Which of the following is a valid window function?COUNT()ROW_NUMBER()SUM()All of these单项选择题

类似问题

Why use a window function instead of GROUP BY for a running total?

You need to calculate the average monthly salary for each department, but you also want to see the individual employee's monthly salary alongside this departmental average, without collapsing the rows. Which of the following SQL queries correctly uses a window function to achieve this?

Given the following query: Which of the following is true about the dept_rank column?

Question at position 42 Window functions can be a part of a calculation within a SELECT statement.TrueFalse

Question at position 1 What is the effect of PARTITION BY in a window function?Combines window frames from multiple tablesDefines groups within the result set for window calculationsSorts rows globallyFilters rows before calculating the window function

Question at position 45 Window functions can be a part of a calculation within a SELECT statement.TrueFalse

Question at position 43 Window functions can be a part of a calculation within a SELECT statement.TrueFalse

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单