如何将nvarchar转换为十进制？

Question

i know how to convert nvarchar to decimal(18,4) Cast method. my tables rows count 80000. My query run perfect below...

SELECT  top 80000 id, Cast(MH as decimal(18,4)) as MH 
FROM TaskRelations WHERE MH is not null

BUT;

but below select query not WORK! if write below:

SELECT   id, Cast(MH as decimal(18,4)) as MH 
FROM TaskRelations WHERE MH is not null

ERROR: Error converting data type nvarchar to numeric.

Answer 1

You have non-numeric data in your MH field after row 80,000.

You can use the ISNUMERIC function but it is notoriously buggy and will give you loads of false positives depending on your data.

Answer 2

The problem is usually that indeed some of the nvarchars in the MH columns are not convertible to decimal.

You can try to inspect the data visually, but as you have more than 80k recordsm, that might not be feasible. Try to inspect the data in some other way - you can use isNumeric , or use group by on the first (or last) three characters of the column, to find the erring data.

Answer 3

Basically the error your receiving is due to the fact that some record past the top 80000 records cannot be converted to decimal. Check your data on all rows > 80000

Answer 4

try this:

SELECT   max(MH) as max_mh, min(mh) as min_mh
FROM TaskRelations 
WHERE MH is not null

the non-numeric values should be lower or higher than the numeric ones.