Trying to understand sqlx::Encode and sqlx::Type

[finlaydotb]

So given a stuct like this

pub struct MyString(String);

and the essential part of using sqlx to bind value of this type

        sqlx::query(query_string)
            .bind(MyString("hi".to_string()))
            .execute(&pool)
            .await?;

This fails with the following compilation error

error[E0277]: the trait bound `MyString: Encode<'_, Postgres>` is not satisfied
  --> src/main.rs:50:19
   |
50 |             .bind(MyString("hi".to_string()))
   |              ---- ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Encode<'_, Postgres>` is not implemented for `MyString`

so I updated the struct to the following

#[derive(sqlx::Encode)]
pub struct MyString(String);

This now shows the error

error[E0277]: the trait bound `MyString: Type<Postgres>` is not satisfied
  --> src/main.rs:50:19
   |
50 |             .bind(MyString("hi".to_string()))
   |              ---- ^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Type<Postgres>` is not implemented for `MyString`

Now I updated the struct to

#[derive(sqlx::Encode, sqlx::Type)]
pub struct MyString(String);

now I get the compilation error

   |
38 | #[derive(sqlx::Encode, sqlx::Type)]
   |          ------------  ^^^^^^^^^^ conflicting implementation for `MyString`
   |          |
   |          first implementation here

Then finally switching it to below compiles

#[derive(sqlx::Type)]
pub struct MyString(String);

But if I now change the struct to something like

pub struct MyTuple((String, String));

I started getting errors about sqlx::Encode and sqlx::Type but this time sqlx::Type does not fix it.

So I am trying now to actually take a step back to actually understands these traits and what they do and how to think/use them.

• So what is the explanation for the errors?
• Why was it that adding the derive for sqlx::Encode and sqlx::Type did not work for the tuple new type?
• I can understand unlike a String there is no obvious way to actually store a tuple into the database - so in this case, if I do not want to split the tuple into database columns, how do I save such values? Save it as JSONB? if so how will that be done?

Answers will be appreciated.