Použijte ROW_NUMBER()
:
SELECT
name,
ROW_NUMBER() OVER (ORDER BY name) AS id
FROM people;
UPRAVIT:
Rozdíl mezi ORDER BY 1
vs 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)
V druhém případě neprobíhá žádná operace řazení.
Druhý dotaz můžete také napsat jako:
SELECT
name,
ROW_NUMBER() OVER () AS id
FROM people;
Proč lidé píší ORDER BY 1
ve funkcích v okně?
Protože v některých dialektech je vyžadováno a ORDER BY 1
funguje jako zástupný symbol.
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;