Question

这可能很简单，但我不是SQL高手，所以我迷路了。我理解sql接受你的查询并按特定顺序执行它，我相信这个查询不起作用的原因：

select * from purchaseorders
where IsNumeric(purchase_order_number) = 1
and cast(purchase_order_number as int) >= 7

所有的buyer_order_number字段都是数字，但我们最近引入了字母数字字段。我想要获得的数据是查看“7”是否大于最高数字purchase_order_number。

Numeric（）函数可以很好地过滤掉字母数字字段，但进行后续的强制转换比较会引发此错误：

Conversion failed when converting the nvarchar value '124-4356AB' to data type int.

我不是在问这个错误意味着什么，这很明显。我问是否有办法在单个查询中完成我想要的东西，最好是因为ORM约束而在where子句中。

Answer 1

这对你有用吗？

select * from purchaseorders
where (case when IsNumeric(purchase_order_number) = 1
       then cast(purchase_order_number as int)
       else 0 end) >= 7

Answer 2

您可以使用子选择

进行选择

select * from (
select * from purchaseorders
where IsNumeric(purchase_order_number) = 1) as correct_orders
where cast(purchase_order_number as int) >= 7

Answer 3

试试这个：

select * from purchaseorders
where try_cast(purchase_order_number as int) >= 7

检查字段是否为数字，然后仅对一个语句中的那些字段执行比较？

3 个答案: