SQLite Forum

use the builtin typeof() function.  This returns the type of the argument:  null, text, blob, integer, real as a text string.

```
sqlite> select typeof(a), a from (select 5/0 as a);
┌───────────┬───┐
│ typeof(a) │ a │
├───────────┼───┤
│ null      │   │
└───────────┴───┘
```

Alternatively, simply see if it is null:

```
sqlite> select case when a is null then 'NaN' else a end from (select 5/0 as a);
┌───────────────────────────────────────────┐
│ case when a is null then 'NaN' else a end │
├───────────────────────────────────────────┤
│ NaN                                       │
└───────────────────────────────────────────┘
```

Or even more simply using the ifnull builtin function:

```
sqlite> select ifnull(a,'NaN') from (select 5/0 as a);
┌─────────────────┐
│ ifnull(a,'NaN') │
├─────────────────┤
│ NaN             │
└─────────────────┘
```

Except, of course, that NULL is a valid value in further arithmetic calculations that will be handled correctly, whereas the text string 'NaN' is not.