> For the complete documentation index, see [llms.txt](https://docs.e6data.com/ingestion-engine/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.e6data.com/ingestion-engine/sql/functions/conditional.md).

# Conditional

*The e6 Ingestion Engine scalar functions are based on* [*Apache DataFusion*](https://arrow.apache.org/datafusion/) *and these docs are derived from the DataFusion function reference.*

| Function                | Description                | Example                         | Result      |
| ----------------------- | -------------------------- | ------------------------------- | ----------- |
| `coalesce(e1, ..., en)` | First non-null value       | `coalesce(NULL, NULL, 'hello')` | `'hello'`   |
| `nullif(e1, e2)`        | NULL if e1 = e2            | `nullif(5, 5)`                  | `NULL`      |
| `nvl(e1, e2)`           | e2 if e1 is NULL           | `nvl(NULL, 'default')`          | `'default'` |
| `nvl2(e1, e2, e3)`      | e2 if e1 not NULL, else e3 | `nvl2('x', 'yes', 'no')`        | `'yes'`     |

## `coalesce`

Returns the first of its arguments that is not *null*. Returns *null* if all arguments are *null*. This function is often used to substitute a default value for *null* values.

```
coalesce(expression1[, ..., expression_n])
```

**Arguments**

* **expression1, expression\_n**: Expression to use if previous expressions are *null*. Can be a constant, column, or function, and any combination of arithmetic operators. Pass as many expression arguments as necessary.

## `nullif`

Returns *null* if *expression1* equals *expression2*; otherwise it returns *expression1*. This can be used to perform the inverse operation of [`coalesce`](#coalesce).

```
nullif(expression1, expression2)
```

**Arguments**

* **expression1**: Expression to compare and return if equal to expression2. Can be a constant, column, or function, and any combination of arithmetic operators.
* **expression2**: Expression to compare to expression1. Can be a constant, column, or function, and any combination of arithmetic operators.

## `nvl`

Returns *expression2* if *expression1* is NULL; otherwise it returns *expression1*.

```
nvl(expression1, expression2)
```

**Arguments**

* **expression1**: return if expression1 not is NULL. Can be a constant, column, or function, and any combination of arithmetic operators.
* **expression2**: return if expression1 is NULL. Can be a constant, column, or function, and any combination of arithmetic operators.

## `nvl2`

Returns *expression2* if *expression1* is not NULL; otherwise it returns *expression3*.

```
nvl2(expression1, expression2, expression3)
```

**Arguments**

* **expression1**: conditional expression. Can be a constant, column, or function, and any combination of arithmetic operators.
* **expression2**: return if expression1 is not NULL. Can be a constant, column, or function, and any combination of arithmetic operators.
* **expression3**: return if expression1 is NULL. Can be a constant, column, or function, and any combination of arithmetic operators.

## `ifnull`

*Alias of* [*nvl*](#nvl)*.*


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