0

I need to select different fields from different databases. One of the field is selecting the maximum of the LastUpdateOn datetime field from different tables.

{Project},{Document},{Instruction},{Document}, {User}, {ProjectParticipant} are the different tables 

SELECT {Project}.[Number],{Project}.[Name],{User}.[Last_Login],{A}.[max_LastUpdatedOn]

From {Project}

INNER JOIN {ProjectParticipant} ON {Project}.[Id] = {ProjectParticipant}.[ProjectId]
INNER JOIN {User} ON {ProjectParticipant}.[UserId] = {User}.[Id] AND {User}.[Username] = @UserId
INNER JOIN {Document} ON {Project}.[Id] = {Document}.[ProjectId]
INNER JOIN {InstructionType} ON {Project}.[Id] = {Instruction}.[ProjectId]
INNER JOIN {Question}  ON {Project}.[Id] = {Question}.[ProjectId]

SELECT MAX(LastUpdatedOn) AS max_LastUpdatedOn
FROM 
(
  SELECT LastUpdatedOn FROM {Question}
  UNION ALL
  SELECT LastUpdatedOn FROM {Document}
  UNION ALL
  SELECT LastUpdatedOn FROM {Instruction}
) A;

GROUP BY {Project}.[Number],
         {Project}.[Name],
         {User}.[Last_Login]
         {A}.[max_LastUpdatedOn]
ORDER BY {Project}.[Number]

But getting an error saying {A} is an unknown entity. I am not sure what is wrong here. Tried using the 

SELECT {Project}.[Number],{Project}.[Name],{User}.[Last_Login],
(SELECT MAX(LastUpdatedOn) as max_LastUpdatedOn
 FROM
 (
  SELECT {Question}.[LastUpdatedOn] where {Project}.[Id] = {Question}.[ProjectId]
  UNION ALL
  Select {Document}.[LastUpdatedOn] where {Project}.[Id] = {Document}.[ProjectId]
  UNION ALL
  SELECT {Instruction}.[LastUpdatedOn] where {Project}.[Id] = {Instruction}.[ProjectId]
  )
  A ) [max_LastUpdatedOn]

 FROM {Project}
 INNER JOIN {ProjectParticipant} ON {Project}.[Id] = {ProjectParticipant}.[ProjectId]
 INNER JOIN {User} ON ({ProjectParticipant}.[UserId] = {User}.[Id] AND {User}.[Username] = @UserId)
 INNER JOIN {Question}  ON {Project}.[Id] = {Question}.[ProjectId]
 INNER JOIN {Document} ON {Project}.[Id] = {Document}.[ProjectId]
 INNER JOIN {Instruction} ON {Project}.[Id] = {Instruction}.[ProjectId]

 GROUP BY {Project}.[Number],
          {Project}.[Name],
          {User}.[Last_Login],
          A.[max_LastUpdatedOn]
 ORDER BY {Project}.[Number]

Getting an error like The multi-part identifier "A.max_LastUpdatedOn" could not be bound.

4

1 回答 1

0

{A}不是 OutSystems 实体，因此您不应使用花括号来引用它。花括号用于将设计时的元模型名称转换为数据库中的物理表名称。

由于A是内部 select 语句的简单别名，因此只需 usingA就足以使其工作。例如：

SELECT {Project}.[Number],{Project}.[Name],{User}.[Last_Login],A.[max_LastUpdatedOn]

更新

关于 的错误The multi-part identifier could not be bound，它与按不在from/join查询源中的内容进行分组有关。

我没有在下面尝试过这段代码，但是这样的事情应该可以解决问题：（
另外，请参阅此处有关如何选择多列的 SQL MAX 的更多方法？）

SELECT {Project}.[Number], {Project}.[Name], {User}.[Last_Login], 
    CASE
        WHEN {Question}.[LastUpdatedOn] >= {Document}.[LastUpdatedOn] AND {Question}.[LastUpdatedOn] >= {Instruction}.[LastUpdatedOn]
        THEN {Question}.[LastUpdatedOn]
        WHEN {Document}.[LastUpdatedOn] >= {Instruction}.[LastUpdatedOn] THEN {Document}.[LastUpdatedOn]
        ELSE {Instruction}.[LastUpdatedOn]
    END AS max_LastUpdatedOn
FROM {Project}
INNER JOIN {ProjectParticipant} ON {Project}.[Id] = {ProjectParticipant}.[ProjectId]
INNER JOIN {User} ON ({ProjectParticipant}.[UserId] = {User}.[Id] AND {User}.[Username] = @UserId)
INNER JOIN {Question}  ON {Project}.[Id] = {Question}.[ProjectId]
INNER JOIN {Document} ON {Project}.[Id] = {Document}.[ProjectId]
INNER JOIN {Instruction} ON {Project}.[Id] = {Instruction}.[ProjectId]
GROUP BY {Project}.[Number], 
         {Project}.[Name], 
         {User}.[Last_Login]
ORDER BY {Project}.[Number]
于 2015-06-29T14:21:11.373 回答