InternalError: (1054, u"Unknown column 't1.pk' in 'field list'")
Can you share your definition of MySqlPrimaryKeyAutoIncrementField ?  Also, it should be MyModel.select().first() (your ex has missing parentheses after select). @coleifer 
.Oh . sorry .(MyModel.select.first(), here is the typo, in my code, I typed the right one  )
```
class MySqlPrimaryKeyAutoIncrementField(BigIntegerField):
    def __init__(self, *args, **kwargs):
        kwargs['primary_key'] = True
        super(MySqlPrimaryKeyAutoIncrementField, self).__init__(*args, **kwargs)

    def __ddl__(self, column_type):
        ddl = super(MySqlPrimaryKeyAutoIncrementField, self).__ddl__(column_type)
        return ddl + [SQL('auto_increment')]
``` I'm really confused. when I use
```
mysql_db = MySQLDatabase('test', host='127.0.0.1', port=3306, user='root', passowrd='root')
```
worked well. In your `__ddl__` method you're not returning anything. That's the issue.
Hi, here is my code. I used the connection pool and created the table, when use MyModel.select.first(), but returns 'InternalError: (1054, u"Unknown column 't1.pk' in 'field list'")', am I doing something wrong? 
```
from playhouse.db_url import connect
mysql_db = connect('mysql+pool://root:root@127.0.0.1:3306/test?max_connections=20&stale_timeout=300')

from promotion_service.store import MySqlPrimaryKeyAutoIncrementField

class MyModel(Model):
    pk = MySqlPrimaryKeyAutoIncrementField()
    other_field = TextField()
    class Meta:
        db_table = 'my_model'
        database = mysql_db
```