SQL
Examples
Create a simple `ENUM` type:  
```sql
CREATE TYPE mood AS ENUM ('happy', 'sad', 'curious');
```  
Create a simple `STRUCT` type:  
```sql
CREATE TYPE many_things AS STRUCT(k INTEGER, l VARCHAR);
```  
Create a simple `UNION` type:  
```sql
CREATE TYPE one_thing AS UNION(number INTEGER, string VARCHAR);
```  
Create a type alias:  
```sql
CREATE TYPE x_index AS INTEGER;
```