Flat to fat：根据条件将sql列转换为多列答案

【问题标题】：Flat to fat: sql column to multiple columns based on conditionFlat to fat：根据条件将sql列转换为多列
【发布时间】：2022-11-10 22:07:05
【问题描述】：

有没有办法创建一个数据透视表，根据一些 if 条件（从平面表到胖表）将单列转换为多列？

CREATE TABLE table_name (A,B,C,D) AS
  SELECT 'A', '1', '4', DATE '2000-01-04' FROM DUAL UNION ALL
  SELECT 'A', '1', '6', DATE '2000-01-04' FROM DUAL UNION ALL
  SELECT 'A', '2', '1', DATE '2000-01-04' FROM DUAL UNION ALL
  SELECT 'B', '1', '20', DATE '2000-01-04' FROM DUAL UNION ALL
  SELECT 'B', '2', '2', DATE '2000-01-04' FROM DUAL UNION ALL
  SELECT 'B', '-3', '999', DATE '2000-01-04' FROM DUAL UNION ALL
  SELECT 'A', '1', '30', DATE '2000-01-05' FROM DUAL UNION ALL
  SELECT 'B', '2', '3', DATE '2001-01-05' FROM DUAL;

每列 A 和 D 的预期结果

A, D, C where B == 1, C where B == 2
A, 2000-01-04, 10, 1
B, 2000-01-04, 20, 2
A, 2000-01-05, 30, 0
B, 2000-01-05, 0, 3

或每列 D

D, C where B == 1 - C where B == 2
2000-01-04, 27
2000-01-05, 27

【问题讨论】：

标签： sql oracle if-statement pivot

【解决方案1】：

你可以做：

select
  a,
  d,
  max(case when b = 1 then c end) as b1,
  max(case when b = 2 then c end) as b2
from table_name
group by a, d

和：

select
  d,
  max(case when b = 1 then c end) -
  max(case when b = 2 then c end) as x
from table_name
group by d

请参阅db<>fiddle 的运行示例。

【讨论】：