December 20, 2024
Data Analyst interview questions for Accenture are as follows :Â
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COUNT
and COUNT DISTINCT
in SQL?COUNT
returns the total number of rows in a table or dataset, including duplicates. COUNT DISTINCT
, however, returns the number of unique (distinct) values in a column, excluding duplicates.UNION
and UNION ALL
in SQL?UNION
combines the results of two queries and removes duplicate rows, while UNION ALL
combines the results without removing duplicates. UNION
is used when we need unique results, while UNION ALL
is used to retain all records, including duplicates.LEFT JOIN
returns all rows from the left table and the matching rows from the right table. If no match is found, NULL values are returned for the right table. A FULL OUTER JOIN
returns all rows from both tables, with NULLs in place where there are no matches.