Update column by looping through rows - sql

Question

I have four columns in a table ID, Longitude, Latitude, and SpatialData. I have the first three columns filled out for every row, but I need to enter in the SpatialData for each row. I can currently manually update the SpatialData column by using the below query:
update GioMap set SpatialData = 'Point(-74.009506 40.70602)' Where ID =1
From here I have to keep manually updating the Longitude, Latitude and ID for every row. I am using this code to try to loop through all of the rows and update the table that way:
DECLARE #LoopC INT = 1, #MaxOID INT,
#Long nVarchar(32), #Lat nVarchar(32),#Col1 nVarchar(11)
SET #MaxOID = (select count(*) from GioMap)
Set #Col1 = 'SpatialData'
WHILE(#LoopC <= #MaxOID)
BEGIN
SET #Long = (Select Longitude FROM GioMap where ID = #LoopC)
SET #Lat = (Select Latitude FROM GioMap where ID = #LoopC)
DECLARE #sql VARCHAR(MAX) = ('update GioMap set ' + #Col1 +' = ' + '''' + 'Point(' + #Long + ' ' + #Lat + ')' + '''' + ' Where ID = ' + #LoopC)
EXEC sp_executesql #sql
SET #LoopC = #LoopC + 1
END
When I run this code I keep getting this error message:
Msg 245, Level 16, State 1, Line 13
Conversion failed when converting the nvarchar value 'update [ISSHXI1].[dbo].[GioMap] set SpatialDat = 'Point(-74.0095 40.706)' Where ID = ' to data type int.
I don't understand why it would be trying to convert it to an int?

Answer 1

You could do something like this:
UPDATE GioMap SET SpatialData = 'Point(' + cast(Longitude as varchar) + ' ' + cast(Latitude as varchar) + ')'

Answer 2

I think the way you are doing it is bad, but that's not technically what you asked.
It is trying to convert it to an int because you are adding a varchar to an int. You need to change this:
DECLARE #sql VARCHAR(MAX) = ('update GioMap set ' + #Col1 +' = ' +
'''' + 'Point(' + #Long + ' ' + #Lat + ')' + '''' + ' Where ID = ' +
#LoopC)
to this
DECLARE #sql VARCHAR(MAX) = ('update GioMap set ' + #Col1 +' = ' +
'''' + 'Point(' + #Long + ' ' + #Lat + ')' + '''' + ' Where ID = ' +
Cast(#LoopC as varchar))

Answer 3

The point statement paramaters need to be seperated by a comma.
DECLARE #sql VARCHAR(MAX) = ('update GioMap set ' + #Col1 +' = ' + '''' + 'Point(' + #Long + ' ' + #Lat + ')' + '''' + ' Where ID = ' + #LoopC)
Instead of:
#Long + ' ' + #Lat + ')
try
#Long + ',' + #Lat + ')
To see what is being executed you can try adding a print statement:
DECLARE #sql VARCHAR(MAX) = ('update GioMap set ' + #Col1 +' = ' + '''' + 'Point(' + #Long + ' ' + #Lat + ')' + '''' + ' Where ID = ' + #LoopC)
print #sql
EXEC sp_executesql #sql
Also why do you parans around strings you are assigning? Its confusing in TSQL. While it works it is jarring and unusual.
Instead of:
SET #MaxOID = (select count(*) from GioMap)
try
SET #MaxOID = 'select count(*) from GioMap'
Later in the code you do both parens and quotes. The great, great majority of TSQL developers just use single quotes.
Ben