Hey guys how are you keeping? I hope everybody is healthy and keep this way in this difficult times.
And to make our life less complicate, here’s another tip. Let’s talk about how to concatenate stuff in Oracle.
Imagine a simple case, we want to query the Planning repository to get the list of UDA’s a member have. We can easily do that by query the HSP_OBJECT, HSP_MEMBER_TO_UDA and HSP_UDA tables.
I’m filtering just 3 products to make it easier for us to see. The results shows that each project has a different number of UDA’s, and we never know how many it’ll be, then the easiest way to concatenate them is to use the command LISTAGG (or WM_CONCAT if you are in a DB version prior to 11.1).
The command is very simple LISTAGG(Column, Separator) WITHIN GROUP (ORDER BY column). As we can see the command allow us to select the separator we want (can be comma or any string really) as well to order the results by another column). Let’s take a look in the example above.
As you can see, it easily create a list split my comma (as specified) for me, and the nice thing about it is that I don’t need to do any string treatment if return null or if I have just one string on it and things like that.
This is an extremely good Function and we heavily use it in ODI to generate dynamic code because its simplicity, for example, we can generate a SQL statement on the fly using the command on source and command on target:
With this results we can easily pass this info to the command on target to generate a dynamic query where ODI will replace the columns we got in the target as well the table name and will also loop for each row we have in the source. This is very handy.
And for the ones that are not in the ORACLE 11.2 and ahead, we can still do that using WM_CONCAT. Is not as powerful as LISTAGG, but works pretty well. Let’s try the first example again:
I cannot show you the results since WM_CONCAT was decommissioned in the 12c (my version), but it’ll work like this. We don’t have the option to choose the separator and to make the string unique and to order by it we need to add DISTINCT in the command WM_CONCAT(DISTINCT column).
I hope that is useful and have a great day.
DEV EPM 