How to take the null values for date,int value in postgresql

Apr 6 2015 6:24 AM

My Update query is

Update tbfacilityreceiptitems set itemID = 9345, Batchno = ' ' , mfgdate = 1/1/2012, expdate = 1/1/2020 , MRP =100.0000, SingleUnitPrice= 80.0000, marginPercentage = 20.00, sellingprice = 80.00, SaletaxID = 30, TaxPercentage = ' ' , TaxPercentage =' ' , SaleTaxPercentage =' ' , SaleTaxType ='' , sellingpricesku ='' where facreceiptitemid = 2291