您希望透视多个列，因此需要在透视表中包含多个列：

SELECT *
FROM   mytable1
PIVOT (
  MAX(descr) AS descr,
  MAX(amount) AS amount,
  MAX(date_paid) AS date_paid
  FOR Invoice IN (
    18  AS INV18,
    100 AS INV100
  )
)
ORDER BY client

字符串
其中，对于样本数据：

CREATE TABLE mytable1 (client, invoice, descr, amount, date_paid) AS
SELECT 123456, 100, 'car',   600, DATE '2020-01-23' FROM DUAL UNION ALL
SELECT 123456,  18, 'truck', 800, DATE '2020-01-29' FROM DUAL UNION ALL
SELECT 123456,   1, 'toy',   500, DATE '2020-01-05' FROM DUAL;

型
产出：
| 客户端|INV18_DESCR| INV 18_数量|INV18_DATE_PAID| INV100_DESCR| INV 100_数量|INV100_DATE_PAID|
| --|--|--|--|--|--|--|
| 123456 |卡车| 800 |2020-01-29 00：00：00|车| 600 |2020-01-23 00：00：00|
fiddle