Oracle从大到小的排名演变（oracle从大到小排名）

Oracle: The Evolution of Ranking from Large to Small

Oracle, the world-renowned database management system, has come a long way since its introduction in 1979. Over the years, it has undergone various enhancements to make it better than ever before. Among these enhancements is the ability to perform sorting and ranking, which is crucial for data analysis.

Sorting data is the process of arranging records in ascending or descending order based on certn criteria. On the other hand, ranking data is a bit more complex. It involves assigning a numerical value to each record based on its position in the sorted result set. This ranking value can then be used to display the records in a particular order.

In earlier versions of Oracle, ranking data was not a strghtforward task. It involved a lengthy and complicated process that was not efficient. However, with the introduction of the Rank and Dense_Rank functions in Oracle 8i, the sorting and ranking process was significantly streamlined.

The Rank and Dense_Rank functions allow you to display the rank of each record in a sorted result set. The rank is determined by the order of the records in the result set, and each record is assigned a unique numerical value. The Dense_Rank function, on the other hand, assigns the same rank to records with the same values.

Let’s take a look at an example to illustrate how these functions work:

SELECT RANK() OVER (ORDER BY salary DESC) AS rank, employee_name, salary
FROM employee_data;

In this example, we are using the Rank function to sort the `employee_data` table based on the `salary` column in descending order. The function assigns a numerical value to each record based on its position in the sorted result set.

The output of the above query will be something like this:

RANK    EMPLOYEE_NAME   SALARY
1       John            10000
2       Jane            8000
3       Mark            7000
4       Brian           6000
5       Sarah           5000
6       Amanda          4000
7       Joe             3000
8       Tom             2000

As you can see from the above output, the Rank function has assigned the rank of each employee based on their salary. John, who has the highest salary, is ranked first, while Tom, who has the lowest salary, is ranked last.

The introduction of the Rank and Dense_Rank functions in Oracle 8i revolutionized the way we sort and rank our data. It has made the process more efficient and less complicated. With the latest version of Oracle, you can further customize the ranking process by using the Partition By clause, which allows you to group records based on a particular column.

In conclusion, Oracle has come a long way since its inception. With every new version, it introduces enhancements that make database management more efficient and less complicated. The Rank and Dense_Rank functions are just one example of this evolution. They have made the sorting and ranking process more effective and customizable, and we can expect Oracle to continue to improve in the future.