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Tip of the day
SQL Server: SQL aliases are used to temporarily rename a table or a column heading
SQL aliases are used to temporarily rename a table or a column heading in queries. Basically aliases are created to make column names more readable.
Aliases can be useful when:
- There are more than one table involved in a query
- Functions are used in the query
- Column names are big or not very readable
- Two or more columns are combined together
- Same Table joining multiple times in one query(like self-join)
- by Venkateswarlu Cherukuru
Question of the day
SQL Server: What is the difference between RANK() and DENSE_RANK() functions?
RANK()
This function does much the same thing as ROW_NUMBER(), only it acknowledges ties in the columns specified in the ORDER BY clause, and assigns them the same rank. Where a tie occurs, the numbers that would otherwise have been "used up" are skipped, and numbering resumes at the next available number. As you can see, RANK() leaves a gap whenever there is a tie.
Ex:-
Marks | 99 | 97 | 93 | 93 | 92 | 91 |
RANK | 1 | 2 | 3 | 3 | 5 | 6 |
DENSE_RANK()
This function doesn't like gaps and doesn't leave any rank if tie occures. DENSE_RANK() "fills in the gaps". It starts from the next number after a tie occurs, so instead of 1, 2, 3, 3, 5, 6 you get 1, 2, 3, 3, 4, 5 for example.
Ex:-
Marks | 99 | 97 | 93 | 93 | 92 | 91 |
DENSE_RANK | 1 | 2 | 3 | 3 | 4 | 5 |
For more details click on Ranking Functions in SQL Server
- by Venkateswarlu Cherukuru
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