Add from_clear to allow emptying current from tables in select statement

[dragonnn]

PR Info

Sea-orm does allow to modify the underlying sea-query statements with can be really useful but sea-query itself doesn't have a way to change the table a SelectStatement is done. This can be really handy when a database has a few tables that do share the same columns but are separated for other reasons, in my use case I have tables like that: data, data_now, data_1s, data_1m. All of them are identical to each other (data_now does have different PK keys, but that isn't important in my case), with using from_clear I can avoid having separate Entities for each table and avoid a lot of boilerplate when mapping them to a single Grpc struct that my backend outputs.

New Features

• add new function to SelectStatement from_clear() with does remove all from statements from it

Changes

• new function from_clear() added to SelectStatement

Let me know if anything more is need in this PR or if you have a better idea to archive what I need for my use case. Or a better name for from_clear() because I am myself not that happy with it.

[tyt2y3]

Just being curious, why not build the same query with different Table passed in as parameters?

[dragonnn]

Just being curious, why not build the same query with different Table passed in as parameters?

Because I am using sea-orm, so I don't build the query myself in the first place. Here is a sample of the code where I am using it:

    pub async fn get_now_by_device_uuid(device_uuid: Uuid, orm: &impl ConnectionTrait) -> DbResult<Option<Self>> {
        let mut query = Entity::find().filter(Column::DeviceUuid.eq(device_uuid));
        sea_orm::QueryTrait::query(&mut query).clear_from().from_as(super::data_now::Entity.table_ref(), Entity);
        query.one(orm).await
    }

Doing the whole query would be for sure more involving as getting the existing sea-orm query and just swapping the table out.

[dragonnn]

If no one has any comments to it I would like to convert from draft to ready :). I would like really to get it merged so I don't have to use my fork in my projects.

[tyt2y3]

Sorry for the delay

[github-actions]

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