# switch


`switch` compares a *condition-expression* with the literal labels, within a set of literal label and *return-expression* pairings. It then returns the *return-expression* corresponding to the first literal label that's equal to the *condition-expression*. If no label equals to the *condition-expression*, `switch` returns the *default-expression*. Every *return-expression* and *default-expression* must have the same datatype.

## Syntax


```
switch(condition-expression, label-1, return-expression-1 [, label-n, return-expression-n ...], 
        default-expression)
```

## Arguments


`switch` requires one or more *if*,*then* expression pairings, and requires exactly one expression for the *else* argument. 

 *condition-expression*   
The expression to be compared with the label-literals. It can be a field name like `address`, a literal value like '`Unknown`', or another scalar function like `toString(salesAmount)`. 

 *label*   
The literal to be compared with the *condition-expression* argument, all of the literals must have the same data type as *condition-expression* argument. `switch` accepts up to 5000 labels. 

 *return-expression*   
The expression to return if the value of its label equals to the value of the *condition-expression*. It can be a field name like `address`, a literal value like '`Unknown`', or another scalar function like `toString(salesAmount)`. All of the *return-expression* arguments must have the same data type as the *default-expression*.

 *default-expression*   
The expression to return if no value of any label arguments equals to the value of *condition-expression*. It can be a field name like `address`, a literal value like '`Unknown`', or another scalar function like `toString(salesAmount)`. The *default-expression* must have the same data type as all of the *return-expression* arguments.

## Return type


`switch` returns a value of the same data type as the values in *return-expression*. All data returned *return-expression* and *default-expression* must be of the same data type or be converted to the same data type. 

## General Examples


The following example returns the Amazon Web Services Region code of input region name. 

```
switch(region_name, 
               "US East (N. Virginia)", "us-east-1", 
               "Europe (Ireland)", "eu-west-1", 
               "US West (N. California)", "us-west-1", 
               "other regions")
```

The following are the given field values.

```
"US East (N. Virginia)"
        "US West (N. California)"
        "Asia Pacific (Tokyo)"
```

For these field values the following values are returned.

```
"us-east-1"
        "us-west-1"
        "other regions"
```

## Use switch to replace `ifelse`


The following `ifelse` use case is an equivalent of the previous example, for `ifelse` evaluating whether values of one field equals to different literal values, using `switch` instead is a better choice.

```
ifelse(region_name = "US East (N. Virginia)", "us-east-1", 
               region_name = "Europe (Ireland)", "eu-west-1", 
               region_name = "US West (N. California)", "us-west-1", 
               "other regions")
```

## Expression as return value


The following example uses expressions in *return-expressions*:

```
switch({origin_city_name}, 
               "Albany, NY", {arr_delay} + 20, 
               "Alexandria, LA", {arr_delay} - 10,
               "New York, NY", {arr_delay} * 2, 
               {arr_delay})
```

The preceding example changes the expected delay time for each flight from a particular city.

![\[An image of the results of the function example, shown in table form.\]](http://docs.amazonaws.cn/en_us/quick/latest/userguide/images/switch-function-example.png)