SQL连接几个表

Question

是的我知道标题中有一些主题，但我真的读了所有这些主题并且无法解决问题。 我在sqlfiddle上显示了一个sql表：http://www.sqlfiddle.com/#!2/0aaf72/1

所以我想要一个这样的结果：

我的意思是我希望所有的数据都是结果，但我得到的是所有的数据，而不是系列列表中写有NULL ...这是我试过的：

SELECT sum(invoiceinput.total) as cons,
   materialtype.`type`,
         materialserie.serie,
         companies.companyName
         FROM invoiceinput JOIN
         invoice ON invoiceinput.invoiceID=invoice.ID JOIN
         companies ON companies.ID=invoice.companiesID JOIN
         materialtype ON materialtype.ID=invoiceinput.materialTypeID LEFT JOIN
         materialserie ON materialserie.ID=invoiceinput.materialTypeID 
         WHERE invoiceinput.materialTypeID 
         GROUP BY materialtype.ID, materialserie.ID, companies.ID, MONTH(21/04/2014)
         ORDER BY MONTH(21/04/2014), companies.ID

Answer 1

SELECT sum(invoiceinput.total) as cons,
   materialtype.`type`,
         materialserie.serie,
         companies.companyName
         FROM invoiceinput JOIN
         invoice ON invoiceinput.invoiceID=invoice.ID JOIN
         companies ON companies.ID=invoice.companiesID JOIN
         materialtype ON materialtype.ID=invoiceinput.materialTypeID LEFT JOIN
         materialserie ON materialserie.ID=invoiceinput.materialserieID 
         WHERE invoiceinput.materialTypeID 
         GROUP BY materialtype.ID, materialserie.ID, companies.ID, MONTH(21/04/2014)
         ORDER BY MONTH(21/04/2014), companies.ID

所以应该有materialserie ON materialserie.ID = invoiceinput.materialserieID而不是materialserie ON materialserie.ID = invoiceinput.materialTypeID