# Comparison functions

Comparison functions select extrema from a list of expressions. They return one of the original values, preserving its type.

`greatest` and `least` skip NULL arguments. The scalar forms of `min` and `max` return NULL if any argument is NULL; their one-argument aggregate forms instead skip NULL rows. Choose the function according to the missing-value behavior you need.

## Example: Comparing optional values

```sql
SELECT greatest(10, NULL, 20), least(10, NULL, 20), max(10, NULL, 20)
FORMAT csv;
```

```text
20,10,\N
```

## greatest

Return the largest non-NULL argument using SQL value ordering and the selected collation.

### Syntax

```text
greatest(value1, ...)
```

### Arguments

One or more SQL values; NULL arguments are skipped. Comparisons follow local SQL value ordering rather than PostgreSQL implicit common-type coercion.

### Returned value

Selected argument with its type preserved; NULL if every argument is NULL.

### Example

```sql
SELECT greatest(1,NULL,3) FORMAT csv;
```

```text
3
```

## least

Return the smallest non-NULL argument using SQL value ordering and the selected collation.

### Syntax

```text
least(value1, ...)
```

### Arguments

One or more SQL values; NULL arguments are skipped. Comparisons follow local SQL value ordering rather than PostgreSQL implicit common-type coercion.

### Returned value

Selected argument with its type preserved; NULL if every argument is NULL.

### Example

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

```text
-2
```

## max

Return the largest of two or more values using SQL value ordering and collation.

### Syntax

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

### Arguments

Two or more SQL values. Any NULL argument makes the result NULL; one argument selects the aggregate form.

### Returned value

The selected input value with its type preserved, or NULL when any argument is NULL.

### Example

```sql
SELECT max(3,1,2) FORMAT csv;
```

```text
3
```

## min

Return the smallest of two or more values using SQL value ordering and collation.

### Syntax

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

### Arguments

Two or more SQL values. Any NULL argument makes the result NULL; one argument selects the aggregate form.

### Returned value

The selected input value with its type preserved, or NULL when any argument is NULL.

### Example

```sql
SELECT min(3,1,2) FORMAT csv;
```

```text
1
```