一个更新语句，总计增加100

Question

我如何编写一份更新声明，为一年中第一年编写的所有发票的发票的信用总额字段增加100？

我试图写一个如下声明：

 Update dbo.invoices
 set credittotal (this is the problem right here where i dont know how to     add       100 to this)
 where invoices = (the first of the year)

Answer 1

添加100意味着列的新值将是当前值加上100：

UPDATE dbo.invoices
SET    credittotal = credittotal + 100
WHERE  DATEPART (dy, invoices) = 1