I found a very strange error in SAS EG, when I run below sas code: PROC SQL; Create table tmp as Select a.id, a.code, b.type From base as a Left join staff as b on a.code=b.code The result tmp dataset will have id value and NULL code and NULL type The data type and value of the code value in table base and staff are correct, but I cannot understand why the value code in table base will become NULL in table tmp. Please help. Thanks Peter
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