From: arne@vajhoej.dk

On 7/28/2025 9:07 PM, Lawrence D'Oliveiro wrote:
> On Mon, 28 Jul 2025 19:28:51 -0400, Arne Vajhøj wrote:
>> I repeat: the saving is not in the query, but in the mapping from the
>> query result to the object model.
>
> But I thought a key point of ORMs is hiding the SQL.

It is not.

The primary point is to save all the code mapping between
query result and object model.

>                                                  Look at SQLAlchemy,
> for example , which
> does a lot of this. Is that a bad example of an ORM?

I prefer SQLModel on top of SQLAlchemy, but ...

Even with ORM you need to express the query.

There are 3 common ways to express a query in
an ORM:
* an ORM specific query language similar to but not identical
   to SQL. Examples: JPQL (Java), HQL (Java), DQL (PHP) etc..
* plain SQL. Example: MyBatis (Java)
* fluent API. Examples: EF (.NET), SQLModel and SQLAlchemy
   (Python)

But even though the ORM framework authors undoubtedly
have strong opinions about that choice, then in the
big picture it does not matter.

JPQL example (ORM specific query language):

List res = em.createQuery("SELECT o FROM T1 AS o WHERE o.f > 0",
T1.class).getResultList();

EF example (fluent API):

List res = db.T1.Where(o => o.F > 0).ToList();

That will both end up executing the SQL:

SELECT * FROM t1 WHERE f > 0

It is fundamentally the same query. Just slightly different
syntax.

SQLAlchemy have chosen the fluent API model.

The big difference in the above two examples compared
to traditional SQL API (JDBC and ADO.NET for Java and .NET)
is that it return a List instead of a generic result
like List.

Arne

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