Question

我运行了以下查询以获取表中的第一行和最后一行。

SELECT Start, End, Start1, End1
FROM
(SELECT Start AS Start, End AS End 
  FROM [TB1]  WHERE Id = 251 ORDER BY DateTime DESC LIMIT 1),
(SELECT Start1 AS Start1, End1 AS End1 
  FROM [TB2]  WHERE Id = 251 ORDER BY DateTime LIMIT 1);

我得到如下输出：

 Start      End      Start1      End1
 25.32      -98.55    null       null
 null       null      29.81      -98.32

我试图以下面的格式获得输出：

 Start      End      Start1      End1
 25.32      -98.55   29.81       -98.32

Answer 1

使用max，结果将在一行。

SELECT max(Start) start, max(End) end, max(Start1) start1, max(End1) end1
FROM
(SELECT Start AS Start, End AS End 
  FROM [TB1]  WHERE Id = 251 ORDER BY DateTime DESC LIMIT 1),
(SELECT Start1 AS Start1, End1 AS End1 
  FROM [TB2]  WHERE Id = 251 ORDER BY DateTime LIMIT 1);

Answer 2

我觉得你的问题是“部分的”，接下来将是如何为所有Id做同样的事情！见下文

SELECT Id, Start, End, Start1, End1
FROM
(SELECT Id, Start, End 
 FROM (
   SELECT
     Id, Start AS Start, End AS END, 
     ROW_NUMBER() OVER(PARTITION BY Id ORDER BY DateTime DESC) AS win
   FROM [TB1])
 WHERE win = 1
) AS t1
JOIN
(SELECT Id, Start1, End1 
 FROM (
   SELECT
     Id, Start1 AS Start1, End1 AS End1,
     ROW_NUMBER() OVER(PARTITION BY Id ORDER BY DateTime) AS win
   FROM [TB2])
 WHERE win = 1
) AS t2
ON t1.Id = t2.Id

Answer 3

如果您希望单个表（而非两个）上的第一行和最后一行，则可以使用ARRAY_AGG ORDER BY和LIMIT standard SQL中的WITH T AS ( SELECT 251 AS Id, 10.0 AS Start, -15 AS `End`, DATE('2016-11-09') AS DateTime UNION ALL SELECT 251, 25.32 AS Start, -98.55, DATE('2016-11-10') UNION ALL SELECT 251, 29.81, -98.32, DATE('2016-01-01') ) SELECT ARRAY_AGG(STRUCT(Start, `End`) ORDER BY DateTime DESC LIMIT 1)[OFFSET(0)] AS first_row, ARRAY_AGG(STRUCT(Start AS Start1, `End` AS End1) ORDER BY DateTime ASC LIMIT 1)[OFFSET(0)] AS last_row FROM T WHERE Id = 251;来计算它（取消选中＆＃34;使用旧版SQL＆＃34;在＆＃34;显示选项＆＃34;在用户界面中）。

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一般来说，这可能比使用分析函数快一点，但我还没有做过任何具体的比较。

查询以获取表中的第一行和最后一行

3 个答案: