# Functions for NULL values

These functions replace missing values or count which arguments are present. SQL NULL is distinct from empty text, numeric zero and a JSON null document.

Use `coalesce` for a fallback value and `num_nulls`/`num_nonnulls` to inspect a row. Use `IS NULL` when the result should be a missing-value predicate.

## Example: Supplying a display fallback

```sql
SELECT coalesce(NULL, 'anonymous') AS display_name,
       num_nulls(NULL, '', 0) AS missing_fields
FORMAT csv;
```

```text
"anonymous",1
```

## coalesce

Return the first non-NULL argument and stop evaluating later arguments.

### Syntax

```text
coalesce(value1, value2, ...)
```

### Arguments

Two or more SQL expressions evaluated from left to right until a non-NULL result is found.

### Returned value

The first non-NULL value with its type preserved; NULL when every argument is NULL.

### Example

```sql
SELECT coalesce(NULL,'fallback') FORMAT csv;
```

```text
"fallback"
```

## num_nonnulls

Count non-NULL arguments.

### Syntax

```text
num_nonnulls(value,...)
```

### Arguments

One or more arguments. Only the outer SQL NULL value is counted as missing.

### Returned value

INTEGER number of non-NULL arguments.

### Example

```sql
SELECT num_nonnulls(1,NULL,2) FORMAT csv;
```

```text
2
```

## num_nulls

Count SQL NULL arguments.

### Syntax

```text
num_nulls(value,...)
```

### Arguments

One or more arguments. Native JSON null and collection members are ordinary non-NULL argument values.

### Returned value

INTEGER number of NULL arguments.

### Example

```sql
SELECT num_nulls(1,NULL,2) FORMAT csv;
```

```text
1
```