How to Assign Row Numbers in PostgreSQL Queries?

Assigning Row Numbers in PostgreSQL Queries

In PostgreSQL, the ability to display observation numbers for each record in a query is enabled through the use of windowing functions. One such function is the row_number() function.

Solution Using row_number()

To show the row numbers, you can use the following syntax:

select row_number() over (order by <field> nulls last) as rownum, *
from <table_name>
order by <field>

Where represents the field by which the rows should be ordered and is the name of the table you're querying from.

Example:

select row_number() over (order by id nulls last) as rownum, *
from employees
order by id

This query will assign sequential row numbers to each record in the employees table, ordered by the id field.

Simplified Solution (When Order Not Required)

If ordering the rows is not necessary, you can simplify the query as follows:

select row_number() over(), *  -- notice: no fields are needed
from <table_name>

This simplified version will assign consecutive row numbers to all rows in the specified table, regardless of the order.

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