SQLAlchemy order_by自定义排序？

Question

I have a state column in my table which has the following possible values: discharged , in process and None .

Can I fetch all the records in the following order: in process , discharged followed by None ?

Answer 1

If you've declared that column as an enum type (as you should for cases such as these where the values are drawn from a small, fixed set of strings), then using ORDER BY on that column will order results according to the order in which the values of the enum were declared. So the datatype for that column should be ENUM('in process', 'discharged', 'None') ; that will cause ORDER BY to sort in the order you desire. Specifically, each value in an enum is assigned a numerical index and that index is used when comparing enum values for sorting purposes. (The exact way in which you should declare an enum will vary according to which type of backend you're using.)