you don't need to repeat all fields during resident load.
The best way to achieve what you want is to create a mapping table with the source string and the new string:
ReplaceTextTable: Mapping Load SourceString, TargetString Inline [ SourceString, TargetString facebook, Facebook face book, Facebook instagram, Instragram ]; Rename field Source as Source_TMP; Rename Table Maintable to Maintable_TMP; Maintable: NoConcatenate Load *, Applymap('ReplaceTextTable',Source_TMP,Source_TMP) as Source Resident Maintable_TMP; Drop Table Maintable_TMP; Drop field Source_TMP;
Using preceding load is a good pratice to achieve this kind of things. You can do someting like :
If(SubStringCount(lower(Source_old),'instagram')=1,'instagram',Source_old)) as Source
Source as Source_old,
other fields ...
FROM YourSourceFile ;
DROP FIELD Source_old;
Edit : You can also use wildmatch(Source_old,'*facebook*')=1 instead of the SubStringCount function