COMPUTER SCIENCE AND ENGINEERING
SQL
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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True
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False
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Either A or B
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None of the above
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Detailed explanation-1: -COUNT(expression) returns the number of values in expression, which is a table column name or an expression that evaluates to a column of data. COUNT(expression) does not count NULL values. This query returns the number of non-NULL values in the Name column of Sample.
Detailed explanation-2: -The COUNT() function returns the number of rows that matches a specified criterion.
Detailed explanation-3: -Note, NULL values are not counted. Count Distinct – whose syntax is COUNTD (expression)-this function returns the number of distinct items in a group. Each unique value is only counted once. Note, NULL values are not counted.
Detailed explanation-4: -The count property directly gives the count of non-NaN values in each column. So, we can get the count of NaN values, if we know the total number of observations.