Several times, so we’re giving it a name to simplify the SQL. In this example you can see that we are reusing the same window definition
Postgresql window functions drivers#
Select surname, position, row_number() over( order by fastestlapspeed:: numeric) as "fastest", ntile( 3) over w as "group", lag(surname, 1) over w as "previous", lead(surname, 1) over w as "next" from results join drivers using(driverid) where raceid = 890 window w as ( order by position) order by position Any such custom aggregate can thenīe given a window frame definition to work against too. You might already know that it’s possible with PostgreSQL to use Sum, min, max, count, avg and the other you’re used to. Window frame rather than a grouping clause, so you can already go use Available window functionsĪny and all aggregate function you already know can be used against a Get to see rows from the available result set of the query. The window functions only happens after the where clause, so you only In a single SQL query we can obtain information from each driver in the raceĪnd add to that other information from the race as a whole. Psql setup displays as the ⦱ character, for convenience. +-+-+-ĭrivers who didn’t finish the race get a null position entry, that our Second time with count(*) gives us how many drivers from the sameĬonstructor participated in the race: surname | name | position | pos same constr The race with respect to other drivers from the same constructor, and the Theįirst time with the row_number() window function gives us the position in That partition twice in the previous SQL query, in the format() call. Results where the constructorid is the same as the current row. The partition by frame allow us to see peer rows, here the rows from Select surname, constructors.name, position, format( '%s / %s', row_number() over(partition by constructorid order by position nulls last), count(*) over(partition by constructorid) ) as "pos same constr" from results join drivers using(driverid) join constructors using(constructorid) where raceid = 890 order by position
0 kommentar(er)
