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ROW_NUMBER() - (MySQL Misc)

The ROW_NUMBER() function is a MySQL Misc function that assigns a unique integer value to each row within the result set of a query. In this tutorial, we will go through the syntax, example, output, explanation, use, and important points of the ROW_NUMBER() function.

Syntax

ROW_NUMBER() OVER (
    [PARTITION BY partition_expression, ... ]
    ORDER BY sort_expression [ASC | DESC], ...
)

Example

Suppose we have a table called "customers" with the following data:

CustomerID Name Age City
1 John Smith 31 New York
2 Jane Doe 27 Los Angeles
3 Joe Schmoe 35 Chicago

We can use the ROW_NUMBER() function to assign a unique integer value to each row in the result set as follows:

SELECT CustomerID, Name, Age, City, ROW_NUMBER() OVER () as RowNum FROM customers;

The above query will return the following result:

CustomerID Name Age City RowNum
1 John Smith 31 New York 1
2 Jane Doe 27 Los Angeles 2
3 Joe Schmoe 35 Chicago 3

Output

The output of the above query will be a table with five columns: CustomerID, Name, Age, City, and RowNum. The RowNum column will contain a unique integer value assigned to each row in the result set.

Explanation

The ROW_NUMBER() function is a window function that assigns a unique integer value to each row within the result set of a query. The function works by partitioning the result set into groups based on the specified partition expressions and then assigning a unique integer value to each row within each group based on the specified sort expressions.

In the example above, we did not specify any partition expressions, which means that the entire result set is considered a single group. We also did not specify any sort expressions, which means that the rows are assigned a unique integer value in an arbitrary order.

Use

The ROW_NUMBER() function is useful in scenarios where we need to assign a unique identifier to each row in a result set. This can be useful in reports and analytics, where we need to reference specific rows within a result set. The function can also be used in conjunction with other window functions to perform complex data manipulations.

Important Points

  • The ROW_NUMBER() function is a window function that assigns a unique integer value to each row within the result set of a query.
  • The function must be used in conjunction with the OVER() clause, which specifies the partition and sort expressions to use when assigning the integer values.
  • If no partition or sort expressions are specified, the function will assign integer values to the rows in an arbitrary order.
  • Window functions are only available in MySQL 8.0 and later versions.

Summary

In this tutorial, we discussed the ROW_NUMBER() function in MySQL and how it can be used to assign a unique integer value to each row within the result set of a query. We covered the syntax, example, output, explanation, use, and important points of the function so that you can use it in your MySQL queries to perform complex data manipulations.

PartitioningCursor
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