使用 UNION ALL 运算符获取忽略 null 的结果

Question

这是我的代码：

select TRANSACTIONID, INFORMATION as "C_cntct", NULL as "C_nam"
from RETAILTRANSACTIONINFOCODETRANS as t
where INFOCODEID = 1009 and TRANSDATE = '2022-07-20'

UNION

select TRANSACTIONID, NULL, INFORMATION
from RETAILTRANSACTIONINFOCODETRANS as t
where INFOCODEID = 1010 and TRANSDATE = '2022-07-20'
group by TRANSACTIONID, INFORMATION
order by TRANSACTIONID, INFORMATION desc

我得到的结果是：

交易ID	C_cntct	C_nam
ST-EMP-ST-LHR-01-66079	拉希德·阿里	NULL
ST-EMP-ST-LHR-01-66079	NULL	0321-9439143
ST-EMP-ST-LHR-01-66080	萨达夫塞哈	NULL
ST-EMP-ST-LHR-01-66080	NULL	0345-4036448

但我想要这个结果，用 Null 忽略：

交易ID	C_cntct	C_nam
ST-EMP-ST-LHR-01-66079	拉希德·阿里	0321-9439143
ST-EMP-ST-LHR-01-66080	萨达夫塞哈	0345-4036448

Answer 1

听起来您需要条件聚合（又名 Pivot），尽管没有样本输入数据很难确定。

通常只使用MIN(CASE WHEN更简单，而不是使用显式的PIVOT语法，这是相当有限的。

SELECT
  trans.TRANSACTIONID,
  MIN(CASE WHEN trans.INFOCODEID = 1009 THEN trans.INFORMATION END) AS C_cntct,
  MIN(CASE WHEN trans.INFOCODEID = 1010 THEN trans.INFORMATION END) AS C_nam
FROM RETAILTRANSACTIONINFOCODETRANS AS trans
WHERE trans.INFOCODEID IN (1009, 1010)
  AND trans.TRANSDATE = '2022-07-20'
GROUP BY
  trans.TRANSACTIONID
ORDER BY
  trans.TRANSACTIONID;