From http://stackoverflow.com/questions/22311427/django-south-migration-cant-cast-the-column-type-wants-me-to-use-using 修改CASE 到END部分 从`sqlmigrate app 0003`中获取sql语句

django_migration_cannot_cast_type.py

# Changing field 'MyTable.associated'
# db.alter_column(u'data_mytable', 'associated', 
#     self.gf('django.db.models.fields.IntegerField')()
# )
db.execute(
    'ALTER TABLE "data_mytable" '
    'ALTER COLUMN "associated" DROP DEFAULT, '
    'ALTER COLUMN "associated" DROP NOT NULL, '
    'ALTER COLUMN "associated" TYPE INTEGER '
    'USING '
    'CASE '
    '  WHEN FALSE THEN 0 ELSE 1 '
    'END'
)