Question

此查询出了什么问题？

它返回： ORA-00904: "PREV_TEMP": invalid identifier

SELECT Id, RecordDate, Temperature, LAG(Temperature) OVER (ORDER BY RecordDate) as prev_temp
FROM Weather
WHERE Temperature > prev_temp;

SQL模式：

Create table If Not Exists Weather (Id int, RecordDate date, Temperature int)
Truncate table Weather
insert into Weather (Id, RecordDate, Temperature) values ('1', '2015-01-01', '10')
insert into Weather (Id, RecordDate, Temperature) values ('2', '2015-01-02', '25')
insert into Weather (Id, RecordDate, Temperature) values ('3', '2015-01-03', '20')
insert into Weather (Id, RecordDate, Temperature) values ('4', '2015-01-04', '30')

Answer 1

您不能直接使用，但需要在子查询中使用才能使用窗口分析函数的返回值

SELECT *
  FROM
  (
   SELECT Id, RecordDate, Temperature, 
          LAG(Temperature) OVER (ORDER BY RecordDate) as prev_temp
     FROM Weather
  )
  WHERE Temperature > prev_temp;

Answer 2

查询的问题在于列别名不能在定义它们的SELECT，WHERE，FROM或GROUP BY子句中重复使用。这适用于窗口功能以及其他所有功能。这是 SQL 的规则，而不是 Oracle 的规则（尽管某些数据库放宽了对GROUP BY的限制）。

在您的情况下，基本上有两种解决方案，一个子查询和一个CTE：

WITH w AS (
      SELECT w.*,
             LAG(Temperature) OVER (ORDER BY RecordDate) as prev_temperature
      FROM weather w
     ) 
SELECT Id, RecordDate, Temperature,  prev_temp
FROM w
WHERE Temperature > prev_temp;

ORA-00904：“ PREV_TEMP”：具有LAG功能的无效标识符

2 个答案: