docs/sql-manual/sql-functions/debug-functions/non-nullable.md

---
{
    "title": "NON_NULLABLE",
    "language": "en"
}
---

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## non_nullable
### description

:::tip
For developer debugging only, do not call this function manually in the production environment.
:::

#### Syntax

`T non_nullable(T expr)`

Raise an error if `expr` is of not nullable, or is of nullable and contains a `NULL` value. Otherwise, returns the non-nullable data column of the input column.

### example

```sql
mysql> select k1, non_nullable(k1) from test_nullable_functions order by k1;
+------+------------------+
| k1   | non_nullable(k1) |
+------+------------------+
|    1 |                1 |
|    2 |                2 |
|    3 |                3 |
|    4 |                4 |
+------+------------------+

mysql> select k1, non_nullable(k1) from test_nullable_functions order by k1;
ERROR 1105 (HY000): errCode = 2, detailMessage = [CANCELLED]There's NULL value in column Nullable(Int32) which is illegal for non_nullable
mysql> select non_nullable(1);
ERROR 1105 (HY000): errCode = 2, detailMessage = [CANCELLED]Try to use originally non-nullable column Int8 in nullable's non-nullable convertion.
```

### keywords
    non_nullable