我正在探索 MLB 棒球 statcast 数据,该数据位于球场级别。我想总结一下车牌外观级别的间距。相关栏目:
game_pk | pitcher_id | batter_id | inning | pitch_number | pitch_type | plt_apprnc_pk (unique)
----------------------------------------------------------------------------------------------
492321 | 542881 | 518466 | 2 | 1 | FF | 4923215428815184662
492321 | 543475 | 571448 | 1 | 2 | SL | 4923215434755714481
492321 | 543475 | 571448 | 1 | 1 | FF | 4923215434755714481
492321 | 543475 | 571448 | 1 | 3 | FF | 4923215434755714481
我正在处理一个查询,仅显示每个板外观的一次迭代 (plt_apprnc_pk),然后是 pitch_number 列(第一个音高、第二个音高、第三个音高等),显示相应音高编号的每种音高类型。本质上,我想通过 pitch_number 转置 pitch_type。
plt_apprnc_pk (unique)| first_pitch | second_pitch | third_pitch
----------------------------------------------------------------
4923215434755714481 | SL | FF | FF
我尝试使用 Case 语句来执行此操作(即 CASE WHEN pitch_number = 1 THEN pitch_type END)。我不断为每个 plt_apprnc_pk 获取多行。
plt_apprnc_pk (unique)| first_pitch | second_pitch | third_pitch
------------------------------------------------------------------
4923215434755714481 | SL | NULL | NULL
4923215434755714481 | NULL | FF | NULL
4923215434755714481 | NULL | NULL | FF
根据 pitch_number 转置这些字符串,同时只保留唯一键的一次迭代的最佳方法是什么??
最佳答案
I tried doing this with Case statements (ie CASE WHEN pitch_number = 1 THEN pitch_type END). I keep getting multiple rows for each plt_apprnc_pk.
这里的模式称为条件聚合:
SELECT plt_apprnc_pk
,MAX(CASE WHEN pitch_number = 1 THEN pitch_type END) AS first_pitch
,MAX(CASE WHEN pitch_number = 2 THEN pitch_type END) AS second_pitch
,MAX(CASE WHEN pitch_number = 3 THEN pitch_type END) AS thrid_pitch
-- ...
--,MAX(CASE WHEN pitch_number = n THEN pitch_type END) AS nth_pitch
FROM tab
GROUP BY plt_apprnc_pk;
注意:必须提前知道最大“pitch_number”。
关于sql - 转置字符串,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/69503873/