如果Field1中的值为null，则从Field2中返回值，否则返回String

Question

Although this seems simple enough, I cannot get it, nor was I able to find what I needed via searching on here. I need this to be done within the builder, or within my SQL code which is already an extremely lengthy bit of code for what the query is doing already. Here is the basis of the issue:

Fields: ItemID | CustomID

If there is a value in CustomID , I'd like to overwrite the ItemID value for that record with a string: "CK"+CustomID .

If the CustomID field is empty for that record, then keep the original ItemID .

I then also need the value for that field to be used to pull the correct data from a linked table. Currently, it will pull the original ItemID 's values for subsequent fields, rather than the string "CK+CustomID" value that would be substituted in place of ItemID .

I thought perhaps an independent subquery would be necessary to discern what the field's value would be, before needing to use that value to gather the subsequent fields from the lookup table.

I am willing to work with the SQL code generated by my query builder, but I am not the greatest with just the code.

Thank you for your help!

Answer 1

Without seeing a sample of the content of your table or linked table, nor knowing the names of either of these tables, I would suggest the following example code:

select * 
from yourlinkedtable t inner join
(
    select iif(t.customid is null, t.itemid, 'CK' & t.customid) as id
    from yourtable t
) q 
on t.itemid = q.id

Here, yourtable represents the table containing the ItemID and CustomID fields, and yourlinkedtable represents the table with which your are looking to match the prefixed ItemID .