how do I update SQL columns with true or false based data in another column on the same table?

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I would like to update 'Supplier' & 'Agent' Columns with either true or false, based on the info in the "Supplier_Agent" column. How would i do this? Also, some records do not have any info in the "Supplier_Agent" column so for them, both 'Supplier' & 'Agent' Columns would be FALSE.