无法将Nvarchar转换为INT

Question

I have two tables called Entry_Data and Data

Entry_Data has three columns:

EntryID DataID DataTypeID

1 50 18

2 49 59

30 28 16

Data has two columns:

DataID Value

50 0x00000000033654

49 Removable

28 E:\\Test.txt

The Value column is an nvarchar field.

I have written a left join while attempting to convert all Value fields that start with 0x to an int so that the Hexadecimal value can be converted into a meaningful and human readable value however I get the error:

Conversion failed when converting the nvarchar value '0x00000000033654' to data type int

SELECT TOP 100
  Entry_Data.DataTypeID AS DataTypeID,
  CAST(Data.Value AS nvarchar(440)) AS Value,
  Data.DataID AS DataID
FROM ActivityLog.Entry_Data
LEFT JOIN ActivityLog.Data
  ON ActivityLog.Entry_Data.DataID =
                                    CASE
                                      WHEN DataTypeID = 18 AND
                                        Value LIKE '%0x%' THEN CONVERT(nvarchar, CONVERT(int, Value, 1))
                                      ELSE DataTypeID
                                    END
WHERE DataTypeID = 18

Answer 1

In your case expression , you are returning an nvarchar for one situation

 THEN CONVERT(nvarchar, CONVERT(int, Value, 1))

and an integer for the second situation

ELSE DataTypeID

You need to correct your join so it always return and int for the join to work.