Operator/operand type mismatch

问题

I'm using the Visual FoxPro OLE DB provider to query a VFP DB and I'm getting:

System.Data.OleDb.OleDbException 'Operator/operand type mismatch`

What could I be doing wrong?

回答1:

In my where clause I had an int on one side and a char(15) on the other side

Table Schema

id int

Query

SELECT *
FROM [some-table]
WHERE id = 'some string'

回答2:

In my case to avoid such kind of inconveniences I do the following I hope it works for you:

var_name = iif(vartype(var_name)=='N',var_name,Val(var_name))

so you avoid two possible errors, if it comes in character with value I convert it into number and if it comes in character without any value it becomes 0.

SELECT *
FROM [some-table]
WHERE id = ?Var_name

来源：https://stackoverflow.com/questions/52809017/operator-operand-type-mismatch