How does the principle of sorting by multiple fields in a database’s ORDER BY work?

2 years ago
Liam
2 minutes

In a database, the ORDER BY statement is used to sort the results of a query. If sorting by multiple fields is needed, you can use multiple field names separated by commas.

The principle of sorting multiple fields is as follows:

  1. Firstly, sort by the first field. The database will sort the query results in ascending or descending order based on the specified field name.
  2. If the values in the first field are the same, then sort by the second field. Sort the values in the second field again to further refine records with multiple identical values.
  3. If there are additional fields for sorting, continue to follow the same principle. The database will sort in the order of multiple fields until all fields are sorted.

Here is an example:
Suppose there is a table called “employees” that includes the following fields:

  1. employee ID
  2. employee name
  3. employee age

To sort employees by age and name, you can use the following SQL query:

SELECT * FROM employees ORDER BY age, name;

First, the records will be sorted by age, and then within the same age group, they will be further sorted by name.

Summary: Sorting by multiple fields is done in the specified order of fields, starting from the first field. If the values of the fields are the same, sorting is then done by the next field until all fields are sorted.

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