这个字段为空写错了？

[bulls5988]

我用过isnull(car_fee_end,0)和isnull(car_fee_end)都提示我错了。

 string fee_sql_card = "select * from car_park_fee where car_fee_nums='" + fee_card_id + "' and datediff(d,car_fee_start,getdate())=0 and isnull(car_fee_end,0)";

[华夏小卒]

isnull(car_fee_end,0)= 没有比较的条件吗

[王向飞]

isnull(car_fee_end,0) = 0

[冷箫轻笛]

isnull(a,b) 的意思是，如果a的值为null，则取b值，这个不能作为条件的

如果作为条件,可以这么写： isnull(a,b) = c

[快溜]

isnull是方法，你写在条件里起什么作用？是不是要判断car_fee_end is null?

[dawugui]

string fee_sql_card = "select * from car_park_fee where car_fee_nums='" + fee_card_id + "' and datediff(d,car_fee_start,getdate())=0 and car_fee_end is null";

[Shawn]

--#1 如果car_fee_nums是数字型的，不用加'
--#2 ISNULL函数的用法看一下联机帮助

string fee_card_id = "1";
string sql = "select * from car_park_fee where car_fee_nums = " + fee_card_id + " and datediff(d,car_fee_start,getdate())=0 and isnull(car_fee_end,0)=0";

[oO寒枫Oo]

......and car_fee_end is null

[cxmcxm]

isnull函数是对字段值进行转换，不是判断是否为null
如果要判断一个字段是否为null,应用is null

//应改为
string fee_sql_card = "select * from car_park_fee where car_fee_nums='" + fee_card_id + "' and datediff(d,car_fee_start,getdate())=0 and car_fee_end is null";

[nothingme45]

是啊. 这是判断 . 怎么成了条件了

[xingheng907]

顶8楼的！

[-晴天]

string fee_sql_card = "select * from car_park_fee where car_fee_nums='" + fee_card_id + "' and datediff(d,car_fee_start,getdate())=0 and car_fee_end is not null";