# COALESCE

The COALESCE function returns the first argument that is not null. If all arguments are null, it returns `null`.

## Syntax

`COALESCE(first, rest)`

### Parameters

#### first

Expression to evaluate.

#### rest

Other expressions to evaluate.

## Examples

Returns the first non-null value between columns `a` and `b`.

```esql
ROW a=null, b="b"
| EVAL COALESCE(a, b)
```
