Python 限制从SQL查询返回无值

我正在使用OdooERP，我想从GenerateSQL查询的字典列表中限制为不返回任何值

form_data = self.read(cr, uid, ids, ['start_date','end_date'], context=context)[0]
sql = "select i.date_invoice, i.number, (select name from res_partner where id=i.partner_id) as partner,i.currency_id, (select name from res_currency where id=i.currency_id) as currency, (select description from account_tax where name=t.name), t.amount, t.base, (t.amount+t.base) as total from account_invoice i, account_invoice_tax t where t.invoice_id = i.id and i.state = 'open' and i.type = 'out_invoice' and i.date_invoice >= '%s' and i.date_invoice <= '%s' order by t.name"%(form_data['start_date'],form_data['end_date']) 

cr.execute(sql)
data = cr.dictfetchall()

上面生成的字典值列表找到了值的描述，并且使用上面的SQL查询得到了“无”结果

form_data = self.read(cr, uid, ids, ['start_date','end_date'], context=context)[0]
sql = "select i.date_invoice, i.number, (select name from res_partner where id=i.partner_id) as partner,i.currency_id, (select name from res_currency where id=i.currency_id) as currency, (select description from account_tax where name=t.name), t.amount, t.base, (t.amount+t.base) as total from account_invoice i, account_invoice_tax t where t.invoice_id = i.id and i.state = 'open' and i.type = 'out_invoice' and i.date_invoice >= '%s' and i.date_invoice <= '%s' order by t.name"%(form_data['start_date'],form_data['end_date']) 

cr.execute(sql)
data = cr.dictfetchall()

我不想要None值，而是想要空字符串或其他空空格空字符串

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我应该如何限制None值？

您需要使用COALESCE postgresql函数处理空值

form_data = self.read(cr, uid, ids, ['start_date','end_date'], context=context)[0]

sql = """
    select 
        i.date_invoice, 
        i.number, 
        (select name from res_partner where id=i.partner_id) as partner,
        i.currency_id, 
        (select name from res_currency where id=i.currency_id) as currency, 
        COALESCE((select description from account_tax where name=t.name), '') as description, 
        t.amount, 
        t.base, 
        COALESCE((t.amount+t.base),0) as total 
from 
    account_invoice i, account_invoice_tax t 
where 
    t.invoice_id = i.id and 
    i.state = 'open' and 
    i.type = 'out_invoice' and 
    i.date_invoice >= '%s' 
    and i.date_invoice <= '%s' 
order by t.name 
"""%(form_data['start_date'],form_data['end_date'])

cr.execute(sql)
data = cr.dictfetchall()

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感谢Emipro技术公司。。我还从奥多论坛得到了不同的解决方案，这可能对某些人有所帮助