Problem with a query using MAX(ID)

I have a query regarding and I think I need to use max ID to get round it.I am creating a query and I need to get the Home Telephone number (from table 3).The problem is that there may be more than one home telephone nuber so I want to get the lastest one (highest ID).

I need to display all the person id from table along with their home no even if it is null.I’m not sure how to get round it whether I do a subquery joining the tables or whether I do a select case.

Please help

Table 1

Person ID

111

112

113

114

207

Table 2

PersonIdID

1110122

1110123

1120124

1130125

2070126

2070127

Table 3

IDTel_noType

01220125 23223Hone

01230122 43533Home

01240122 444111Mobile

0125077747474Mobile

012601222747474Home

012701232484848Home

Result

Person IDHome No

1110122 43533

112NULL

113NULL

114NULL

20701232 484848

use the following query...

Code Snippet

Create Table #table1 (

[PersonId] Int

);

Insert Into #table1 Values('111');

Insert Into #table1 Values('112');

Insert Into #table1 Values('113');

Insert Into #table1 Values('114');

Insert Into #table1 Values('207');

Create Table #table2 (

[PersonId] int ,

[ID] int

);

Insert Into #table2 Values('111','0122');

Insert Into #table2 Values('111','0123');

Insert Into #table2 Values('112','0124');

Insert Into #table2 Values('113','0125');

Insert Into #table2 Values('207','0126');

Insert Into #table2 Values('207','0127');

Create Table #table3 (

[ID] int ,

[Tel_no] Varchar(100) ,

[Type] Varchar(100)

);

Insert Into #table3 Values('0122','0125 23223','Hone');

Insert Into #table3 Values('0123','0122 43533','Home');

Insert Into #table3 Values('0124','0122 444111','Mobile');

Insert Into #table3 Values('0125','0777 47474','Mobile');

Insert Into #table3 Values('0126','01222 747474','Home');

Insert Into #table3 Values('0127','01232 484848','Home');

Select

X.PersonId

,Tel_No

,Y.ID

,Type Into #Temp

From

#Table1 X

Left Outer Join #Table2 Y On X.Personid=Y.PersonID

Left Outer Join #Table3 Z on Z.Id=Y.ID

Select

A.PersonId

,B.Tel_No as Home_No

from

(Select PersonId, Max(Case When Type='Home' Then Id Else NULL END) ID

From #Temp Group By PersonId) A

Left Outer Join #Temp B On A.PersonId=B.PersonId And A.id=B.ID

Select

A.PersonId

,B.Tel_No as Mobile_No

from

(Select PersonId, Max(Case When Type='Mobile' Then Id Else NULL END) ID

From #Temp Group By PersonId) A

Left Outer Join #Temp B On A.PersonId=B.PersonId And A.id=B.ID

Select Home.PersonId,Home_No,Mobile_No from

(

Select

A.PersonId

,B.Tel_No as Home_No

from

(Select PersonId, Max(Case When Type='Home' Then Id Else NULL END) ID

From #Temp Group By PersonId) A

Left Outer Join #Temp B On A.PersonId=B.PersonId And A.id=B.ID

) as Home

Join

(

Select

A.PersonId

,B.Tel_No as Mobile_No

from

(Select PersonId, Max(Case When Type='Mobile' Then Id Else NULL END) ID

From #Temp Group By PersonId) A

Left Outer Join #Temp B On A.PersonId=B.PersonId And A.id=B.ID

) as Mobile

On Home.PersonId=Mobile.PersonId

|||Here are two versions, one for SQL Server 2005 and later, and one for SQL Server 2000 and earlier:

-- Requires SQL Server 2005 or later
with TPRanked as (
select
T1.PersonId,
T3.Tel_no,
rank() over (
partition by T1.PersonId
order by T2.ID desc
) as rk
from #table1 as T1 left outer join #table2 as T2
on T2.PersonId = T1.PersonId
left outer join #table3 as T3
on T3.ID = T2.ID
and T3.Type = 'Home'
)
select
PersonId,
Tel_no
from TPRanked
where rk = 1

-- SQL Server 2000 or 7.0
select
T1.PersonId,
T3.Tel_no
from #table1 as T1 left outer join #table2 as T2
on T2.PersonId = T1.PersonId
left outer join #table3 as T3
on T3.ID = T2.ID
and T3.Type = 'Home'
where not exists (
select *
from #table1 as T1a left outer join #table2 as T2a
on T2a.PersonId = T1a.PersonId
left outer join #table3 as T3a
on T3a.ID = T2a.ID
and T3a.Type = 'Home'
where T1a.PersonId = T1.PersonId
and T2a.ID > T2.ID
)

Steve Kass
Drew University
http://www.stevekass.com
|||I have just tried the above query in SQL but the problem is that it will show a NULL value if a mobile no has a higher ID than a Home no.|||

I need to do the query without creating any temporary tables.

|||

Ok.. here it is..

Note: If you use temp table then you can increase the performance

Code Snippet

Create Table #table1 (

[PersonId] Int

);

Insert Into #table1 Values('111');

Insert Into #table1 Values('112');

Insert Into #table1 Values('113');

Insert Into #table1 Values('114');

Insert Into #table1 Values('207');

Create Table #table2 (

[PersonId] int ,

[ID] int

);

Insert Into #table2 Values('111','0122');

Insert Into #table2 Values('111','0123');

Insert Into #table2 Values('112','0124');

Insert Into #table2 Values('113','0125');

Insert Into #table2 Values('207','0126');

Insert Into #table2 Values('207','0127');

Create Table #table3 (

[ID] int ,

[Tel_no] Varchar(100) ,

[Type] Varchar(100)

);

Insert Into #table3 Values('0122','0125 23223','Hone');

Insert Into #table3 Values('0123','0122 43533','Home');

Insert Into #table3 Values('0124','0122 444111','Mobile');

Insert Into #table3 Values('0125','0777 47474','Mobile');

Insert Into #table3 Values('0126','01222 747474','Home');

Insert Into #table3 Values('0127','01232 484848','Home');

Select

A.PersonId

,B.Tel_No as Home_No

from

(Select PersonId, Max(Case When Type='Home' Then Id Else NULL END) ID

From (Select

X.PersonId

,Tel_No

,Y.ID

,Type

From

#Table1 X

Left Outer Join #Table2 Y On X.Personid=Y.PersonID

Left Outer Join #Table3 Z on Z.Id=Y.ID) as D Group By PersonId) A

Left Outer Join (Select

X.PersonId

,Tel_No

,Y.ID

,Type

From

#Table1 X

Left Outer Join #Table2 Y On X.Personid=Y.PersonID

Left Outer Join #Table3 Z on Z.Id=Y.ID) B On A.PersonId=B.PersonId And A.id=B.ID

|||I think I have a corrected query for SQL Server 2005. I changed the ranking criteria so that 'Home' numbers are always ranked highest. I'm working on the 2000 query. Obviously this needs careful testing!

with TPRanked as (
select
T1.PersonId, T2.ID,
T3.Tel_no,
rank() over (
partition by T1.PersonId
order by
case when T3.Type = 'Home' then 0 else 1 end,
T2.ID desc
) as rk
from #table1 as T1 left outer join #table2 as T2
on T2.PersonId = T1.PersonId
left outer join #table3 as T3
on T3.ID = T2.ID
and T3.Type = 'Home'
)
select
PersonId,
Tel_no
from TPRanked
where rk = 1

SK
|||Here's a correction for SQL 2000 along with another query that takes a different approach. The different approach doesn't generalize very well, but it's much more concise.

-- Quick and dirty
select
T1.PersonId,
(
select top (1) Tel_no
from #table2 as T2
join #table3 as T3
on T3.ID = T2.ID
and T3.Type = 'Home'
where T2.PersonId = T1.PersonId
order by T3.ID desc
) as Tel_no
from #table1 as T1

-- Second try, first approach
select
T1.PersonId,
T3.Tel_no
from #table1 as T1 left outer join #table2 as T2
on T2.PersonId = T1.PersonId
left outer join #table3 as T3
on T3.ID = T2.ID
and T3.Type = 'Home'

where not exists (
select *
from #table1 as T1a left outer join #table2 as T2a
on T2a.PersonId = T1a.PersonId
left outer join #table3 as T3a
on T3a.ID = T2a.ID
and T3a.Type = 'Home'
where T1a.PersonId = T1.PersonId
and (
(T3a.Type = 'Home' and (T3.Type is null or T2a.ID > T2.ID)) or
(T3.Type is null and T2a.ID > T2.ID)
)
)

SK

Problem when creating FK

Hello everyone,

I'm created a new SQL Server 2005 database for a new project and I'm facing a little situation regarding FKs. I guess that's what you get when you move from MySql 4 to Sql Server 2005 ;)

Here's the situation: I have a table called contact, assigned to the schema person, and that table handles all the base information regarding users. Informations such as FirstName, LastName, etc, are stored in the [Person].[Contact]. So far so good.

As a design decision I've decided to keep track of the nick names (Alias) that a given member had over-time. In order to do this I've designed the [Person].[GlobalAlias] table like this:

Id uniqueidentifier [NOT NULL] [PK]
ContactId uniqueidentifier [NOT NULL] [FK Person.Contact Id]
Alias nvarchar(30) [NOT NULL]
AddedByContactId uniqueidentifier [NOT NULL] [FK Person.Contact Id]
AddedDate datetime [NOT NULL]
AddedObs nvarchar(MAX) [NULL]
RemovedByContactId uniqueidentifier [NULL] [FK Person.Contact Id]
RemovedDate datetime [NULL]
RemovedObs nvarchar(MAX) [NULL]
ModifiedDate datetime [NOT NULL]
Status bit [NOT NULL]

This table seems to work great dispite the fact that it generates an error when I try to set the FKs. For the column [Person].[GlobalAlias] ContactId I set a FK to the column [Person].[Contact] Id with cascade on delete and on update. Now, when I go to the [Person].[GlobalAlias] AddedByMembershipId and try to add a FK to the column [Person].[Contact] Id it works as long as I define NO ACTION on delete and on update. Obviously, this could originate rows where the [Person].[Contact] that added a [Person].[GlobalAlias] was deleted and there's still a reference to that ID in the [Person].[GlobalAlias] AddedByMembershipId

Here's the error that I'm getting from the database:

'Contact (Person)' table saved successfully
'GlobalAlias (Person)' table
- Unable to create relationship 'FK_GlobalAlias_AddedByContactId_Contact_Id'.
Introducing FOREIGN KEY constraint 'FK_GlobalAlias_AddedByContactId_Contact_Id' on table 'GlobalAlias' may cause cycles or multiple cascade paths. Specify ON DELETE NO ACTION or ON UPDATE NO ACTION, or modify other FOREIGN KEY constraints.
Could not create constraint. See previous errors.

How could I solve this? Perhaps the only way is to normalize it even further and create a history table?

Best regards,
DBA

That is pretty much what you appear to have now. Just that you are trying to set up foreign key relationships into it, which you probably shouldn't.

With a cascading delete, if you deleted someone, the delete would want to then cascade to every record in your GlobalAlias table that referenced them (Every alias they ever had, and any alias's they had ever created for someone else, or removed from someone else). That probably isn't what you wanted. I could see possibly wanting the updates to cascade, but you normally don't want users to be able to change their uid, so the FK really isn't all that useful for cascading updates.