Srini,
Here's the explanation that I received from the dev team:
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Basically, whatever is in the fixed value column gets called in the SQL select for either the datapump ,CTAS or update scripts.
So for example if it is a fixed value of ‘FIXED’ then the SQL for a table with col1, col2 and col3 looks like
SELECT COL1,
COL2,
‘FIXED’
FROM table
If there is a user defined function that can be called from SQL, then this can be added in the fixed value column instead and it will be added to the SQL automatically.
For example if I have a function ADD that adds the values of 2 columns, then I would need to put this in the fixed value column together with its arguments, so ADD(COL1, COL2)
Then the SQL becomes
SELECT COL1,
COL2,
ADD(COL1, COL2)
FROM table
The update becomes:
UPDATE table SET COL3 = ADD(COL1, COL2)
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In your case, standard SQL should do the trick as noted previously:
CONCAT(SUBSTRING(CARD_NO,1,6),'999999',SUBSTRING(CARD_NO,13,4))
Replace CARD_NO with your column name and this should mask as desired.
Hope that helps.