SQL Server的行号变更之路（行号 sqlserver）

SQL’s row numbering is one of the most common and often necessary tasks that must be performed. It is a fundamental building block for many types of data analysis, sorting, and analysis. Fortunately, there are a few ways to easily and quickly modify or change a row’s number in SQL Server.

The simplest option available is using the ROWNUMBER() function. This command can be used to add a row number to every row in a given result set. It is immensely useful in situations where a unique identifier (such as an order number) needs to be assigned to each row. An example of the ROWNUMBER() function in action is shown below.

“`sql

SELECT ROW_NUMBER() OVER (ORDER BY [column name]) AS [new row#]

FROM your_table;

This will create a new column with a series of numbers, starting at one and incrementing by one for each row.

The logic of the ROW_NUMBER() method is quite simple, but it does have a few drawbacks. Firstly, due to the simple logic of the command, it is easy for the numbers to become out of order. This can be addressed by using the PARTITION BY clause, which will reset the numbering for specific groups.

Another option is to use the IDENTITY() function to create a distinct, automatically-incremented field. This allows the data in a table to be more easily sorted, divided into groups, and queried. Identity is often used in conjunction with primary keys in order to add numerical values to fields such as short strings. The IDENTITY() command is shown below.

```sql
CREATE TABLE tablename
(
    id int IDENTITY(1,1),
    column_1 varchar(50)
);

This command will create a table with an integer column that will automatically increment by one for every record inserted.

Finally, it is possible to create a column of consecutive row numbers without using any function at all. This technique, which is known as “window ranking” involves creating a temporary table with an identity column, inserting the desired data into it, and then joining it to the existing table. This method can be significantly more efficient than using the ROW_NUMBER() or IDENTITY() functions if the data set is large.

In summary, there are multiple ways to modify or change a row’s number in SQL Server. The ROW_NUMBER() and IDENTITY() functions are simple and reliable, while the window ranking technique can be faster and more efficient for large datasets. Whichever method is used, it is important to clearly understand the sequence of operations required to achieve the desired result.