sql update table set - The multi-part identifier could not be bound

Question

I have 2 tables:

• Table1 = names of gas stations (in pairs)
• Table2 = has co-ordinate information (longitude and latitude amongst other things)

Example of Table1:

StationID1  StationID2  Name1   Name2   Lattitude1  Longitude1  Lattitude2  Longitude2  Distance
------------------------------------------------------------------------------------------------
93353477    52452   FOO     BAR     NULL        NULL        NULL    NULL    NULL
93353527    52452   HENRY   BENNY   NULL        NULL        NULL    NULL    NULL
93353551    52452   GALE    SAM     NULL        NULL        NULL    NULL    NULL

Example of Table2:

IDInfo     Name  Lattitude    Longitude
-------------------------------------------
93353477   BAR   37.929654    -87.029622

I want to update this table with the coordinate information which resides in tableA. I tried to do the following as per SQL Server 2005: The multi-part identifier … could not be bound

update table1
set t1.[Lattitude1] = t2.[Lattitude]
from table1 t1
left join table2 t2 
on (t1.StationID1 = t2.IDInfo)

I get the following error message:

Msg 4104, Level 16, State 1, Line 1
The multi-part identifier "t1.Lattitude1" could not be bound.

However, if I do the following it works which I can then store into another table.

SELECT t1.[StationID1]
      ,t1.[StationID2]
      ,t1.[Name1]
      ,t1.[Name2]
        ,t2.[Lattitude] AS [Lattitude1]
        ,t2.[Longitude] AS [Longitude1]
        ,t3.[Lattitude] AS [Lattitude2]
        ,t3.[Longitude] AS [Longitude2]
from table1 t1
left join table2 t2 
on (t1.StationID1 = t2.IDInfo)
left join table2 t3 
on (t1.StationID2 = t2.IDInfo)

I am very new to SQL and am having a difficult time understanding why some things work and others don't. Based on the link I posted above my initial query should have worked - no? Perhaps I'm not thinking straight as I have spent many hours trying this and I finally got help from a co-worker (she suggested the approach I mention above).

Answer 1

I think you can modify your UPDATE statement to reference the table alias in the UPDATE line.

update t1
set t1.[Lattitude1] = t2.[Lattitude]
from table1 t1
left join table2 t2 
on (t1.StationID1 = t2.IDInfo)

Answer 2

You need to change the inner table and give a different allias to the columns that are similar. This should work.

update table1
set [Lattitude1] = x.[lat]
from 
(
    SELECT IDInfo [id], Lattitude [lat] FROM 
    table2
) x
WHERE
StationID1 = x.[id]

In your particular case its not necessary to rename Lattitude to lat, but if you end up updating a table with itself and force yourself into giving the columns different names, it will save you headaches down the road.