How can I Show Row Numbers in PostgreSQL Query Results?

Show Row Numbers in PostgreSQL Query

Question:

How can I display the row number for each record retrieved by a PostgreSQL query? Understanding windowing functions in PostgreSQL 8.4 would be helpful.

Answer:

PostgreSQL offers two methods to add row numbers to query results:

1. row_number() over () Window Function:

This function returns the sequential row number for each record. The order of rows in the result set is determined by the specified ordering clause (e.g., row_number() over (order by nulls last) as rownum). This method allows for custom ordering and handling of NULL values.

2. row_number() over () with No ORDER BY Clause:

If the order of rows is not significant, you can simplify the query by omitting the order by clause. This will assign sequential row numbers to all records in the result set.

Syntax for both methods:

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

Example:

SELECT row_number() over (order by id nulls last) as rownum, *
FROM users
ORDER BY id;

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