Använd ROW_NUMBER()
:
SELECT
name,
ROW_NUMBER() OVER (ORDER BY name) AS id
FROM people;
EDIT:
Skillnad mellan ORDER BY 1
kontra ORDER BY column_name
SELECT
name,
ROW_NUMBER() OVER (ORDER BY name) AS id
FROM people;
/* Execution Plan */
QUERY PLAN WindowAgg (cost=83.37..104.37 rows=1200 width=38)
-> Sort (cost=83.37..86.37 rows=1200 width=38)
**Sort Key: name**
-> Seq Scan on people (cost=0.00..22.00 rows=1200 width=38)
SELECT
name,
ROW_NUMBER() OVER (ORDER BY 1) AS id
FROM people;
/* Execution Plan */
QUERY PLAN WindowAgg (cost=0.00..37.00 rows=1200 width=38)
-> Seq Scan on people (cost=0.00..22.00 rows=1200 width=38)
I det andra fallet finns det ingen sorteringsoperation.
Du kan också skriva den andra frågan som:
SELECT
name,
ROW_NUMBER() OVER () AS id
FROM people;
Varför människor skriver ORDER BY 1
i fönsterfunktioner?
För i vissa dialekter krävs det och ORDER BY 1
fungerar som platshållare.
Oracle:
SELECT
name,
ROW_NUMBER() OVER (ORDER BY 1) AS id
FROM people;
TSQL:
SELECT
name,
ROW_NUMBER() OVER (ORDER BY (SELECT 1)) AS id
FROM people;