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pivot.md

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Pivot in BigQuery

View interactive notebook here

Description

Pivoting data is a helpful process of any analysis. Recently BigQuery announced a new PIVOT operator that will make this easier than ever.

SELECT 
   <COLS>
FROM
   <TABLE>
PIVOT(<AGG_FN>(<AGG_COL>) FOR <PIVOT_COL> IN (<val1> [as alias], <val2> [as alias], ... <valn> [as alias]) [as alias]

where:

  • anything in brackets is opional
  • <COLS> is the list of columns returned in the query
  • <TABLE> is the table you a pivoting
    • may not produce a value able or be a subquery using SELECT AS STRUCT
  • <AGG_FN> is an aggregate function that aggregates all input rows across the values of the <PIVOT_COL>
    • may reference columns in <TABLE> and correlated columns, but none defined by the PIVOT clause itself
    • must have only one argument
    • Except for COUNT, you can only use aggregate functions that ignore NULL inputs
    • if using COUNT, you can use * as an argument
  • <AGG_COL> is the column that will be aggregated across the values of <PIVOT_COL>
  • <PIVOT_COL> is the column that will have its values pivoted
    • values must be valid column names (so no spaces or special characters)
    • use the aliases to ensure they are the right format

Example

In this case we'll see how many matches some popular tennis players have won in the Grand Slams.

--tennis_data
select 
  winner_name,
  count(1) wins, 
  initcap(tourney_name) tournament
from 
  tennis.matches_partitioned
where winner_name in ('Novak Djokovic','Roger Federer','Rafael Nadal','Serena Williams')
and tourney_level = 'G'
group by winner_name, tournament
winner_name wins tournament
Roger Federer 91 Us Open
Roger Federer 103 Australian Open
Roger Federer 102 Wimbledon
Roger Federer 70 Roland Garros 
select * 
from 
  tennis_data 
  pivot(sum(wins) for tournament in ('Wimbledon','Us Open' as US_Open,'Roland Garros' as French_Open,'Australian Open' as Aussie_Open ))
winner_name Wimbledon US_Open French_Open Aussie_Open
Roger Federer 102 91 70 103

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