如果其他字段没有值，如何在mysql join语句中显示所有字段

Question

下面脚本仅显示他们在表issuemail和amount上拥有的数据。我希望所有的数据都应该显示的表发出邮件和金额将成为0，如果这不在金额表中。1.卡号和条码在出库表中是唯一的，不会repeat...........on金额卡号可以重复，但卡号和条码不会同时重复

Select issuemail.borrowernumber,
  issuemail.cardnumber,
  issuemail.firstname,
  issuemail.surname,
  issuemail.title,
  issuemail.author,
  issuemail.barcode,
  issuemail.issuedate,
  issuemail.date_due,
  amount.amount
From issuemail Inner Join
  amount On amount.cardnumber = issuemail.cardnumber And amount.barcode =
    issuemail.barcode 

Answer 1

尝试使用左连接instead..Like

    Select issuemail.borrowernumber,
    issuemail.cardnumber,
    issuemail.firstname,
    issuemail.surname,
    issuemail.title,
    issuemail.author,
    issuemail.barcode,
    issuemail.issuedate,
    issuemail.date_due,
    amount.amount
    From issuemail Left Join
    amount On amount.cardnumber = issuemail.cardnumber And amount.barcode =
    issuemail.barcode