User has some constraint written for the repository including expression like tablesql(tableSql({ link_LOCATION_MASTER.LOC_TYP }, where ( link_LOCATION_MASTER.PRODUCTID = PRODUCTID ) )), while deployment or exporting particular rulebase, the studio throws below error:
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com.tibco.mdm.ui.common.exceptions.TransformationException: Error while parsing Constraint:Fetch_LOC_TYP: , please correct the expression in assign Action component name: null
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For reference, I have attached the error screenshot from the studio.

The error states that the defined tablesql expression has some parsing errors. But, in reality, the reason for the issue is different.

If MDM project consist following types of the files in Rulebase Models folder -

rbworkitemdescription.xml
RulebaseCustomFunction.class
RulebaseCustomFunction.java

Then, while export or deployment the studio will throw above error.

Studio throwing exception while deploying/exporting rulebase.

Product: TIBCO MASTER DATA MANAGEMENT Version: 9.1.0 or Higher Business Studio: 5.1.0 HF-01 OS: Windows

The reason is, while export/deployment, code expects only .rul file in this folder and it fails to scan other types of files.

So, to resolve the error please delete the extra files from the rulebase models folder, and try to deploy or export. It will not throw any parsing or NPE error.