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从类型“dbnull”到类型“integer”的强制转换无效

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从类型“dbnull”到类型“integer”的强制转换无效[已结贴,结贴人:wx_zl]

发表于：2007-01-06 14:23:23 楼主

定义了个函数 public function runcard_query（byval strtype as string, byval strdate as string, byval strclass as string) as dataset
dim data as new dataset（)
dscommand.selectcommand = new sqlcommand（ "select max（cast（substring（runcard,2,9) as integer)) as num from runcard where type = ' " + strtype + " ' and classname = ' " + strclass + " ' and runcard like ' " + strdate + " ' + '% ' ", con)
'dscommand.selectcommand = new sqlcommand（ "select count（*) as num from runcard where type = ' " + strtype + " ' and classname = ' " + strclass + " ' and runcard like ' " + strdate + " ' + '% ' ", con)
dscommand.fill（data)
runcard_query = data
end function
引用 ds = mysqldata.runcard_query（ "wafer_lot ", strdate, "pro ")
dim i as integer
dim j as integer

i = ds.tables（0).rows（0)（ "num ")

j = i + 1
……
结果运行就说从类型“dbnull”到类型“integer”的强制转换无效,请高手指教,急!!!

发表于：2007-01-06 14:38:251楼得分:10

select isnull（max（cast（substring（runcard,2,9) as integer)),0) as num from runcard where type ...

发表于：2007-01-06 19:47:092楼得分:0

if（isdbnull（ds.tables（0).rows（0)（ "num ")),0,ds.tables（0).rows（0)（ "num ") )

发表于：2007-01-06 19:47:243楼得分:0

j=iif（isdbnull（ds.tables（0).rows（0)（ "num ")),0,ds.tables（0).rows（0)（ "num ") )

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