sql-macros 0.2.0

Auto generate sql queries for CRUD on sqlx
Documentation
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<!-- markdownlint-disable MD033 -->

# Crate sql-macros

`sql-macros` - it's simple lib for generate sql query for select, select_many, select_all, insert, update, delete

## 0.2 changes

The attribute parser was rewritten from a hand-rolled `TokenTree` walker onto
[`darling`](https://crates.io/crates/darling), on `syn` 3.0. This fixes a
couple of real bugs (field types with 0 or 2+ generic arguments used to be
silently dropped during codegen; `SqlInsertMany` didn't actually batch-insert
anything) and replaces `panic!`s with span-accurate compile errors.

**Breaking change:** `#[table(name = users)]` (bare identifier) is no longer
accepted — write `#[table(name = "users")]` instead. This is the only syntax
change; `return_type = User`, `select = method(field1, field2)`,
`as_type = "..."`, `spec_columns = "..."`, and `return_fields = "..."` are
all unchanged. `SqlInsertMany` now does a real multi-row `INSERT ... VALUES
(...), (...), ...` via `sqlx::QueryBuilder` instead of silently discarding
the query result, and `#[table(update = name(fields))]` (multiple
differently-filtered `update` methods per struct) is now supported — see
[Insert many](#insert-many) and [Generate methods with many fields](#generate-methods-with-many-fields).

## Install

```toml
# Cargo.toml
[dependencies]
sql-macros = { version = "0.2" }
```

## Usage

## Table name

```rust
use sql_macros::SqlSelect;

#[derive(SqlSelect)]
pub struct User {
    #[table(select)]
    pub id: i32,
    pub email: String,
}
```

Table name will be generated as `users`

If you need use special name use `#[table(name = "users")]`

## Select one

```rust
use sql_macros::SqlSelect;

#[derive(SqlSelect)]
pub struct User {
    #[table(select)]
    pub id: i32,
    pub email: String,
}

pub async fn get_by_id(pool: &sqlx::PgPool, id: i32) -> Result<Option<User>, sqlx::Error> {
    let user = User::select_by_id(pool, id).await?;
    Ok(user)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT id, email FROM users WHERE id=$1"]
    pub async fn select_by_id(pool: &sqlx::PgPool, id: i32) -> Result<Option<User>, sqlx::Error> {
        let object = sqlx::query_as!(User, "SELECT id, email FROM users WHERE id=$1", id)
            .fetch_optional(pool)
            .await?;
        Ok(object)
    }
}
```

</details>

## Select all

```rust
use sql_macros::SqlSelectAll;

#[derive(SqlSelectAll)]
pub struct User {
    pub id: i32,
    pub email: String,
}
pub async fn get_all_users(pool: &sqlx::PgPool) -> Result<Vec<User>, sqlx::Error> {
    let users = User::select_all(pool).await?;
    Ok(users)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT id, email FROM users"]
    pub async fn select_all(pool: &sqlx::PgPool) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(User, "SELECT id, email FROM users")
            .fetch_all(pool)
            .await?;
        Ok(object)
    }
}
```

</details>

## Select many

```rust
use sql_macros::SqlSelectMany;

#[derive(SqlSelectMany)]
pub struct User {
    pub id: i32,
    pub email: String,
    #[table(select_many)]
    pub is_removed: bool,
}
pub async fn get_by_removed(pool: &sqlx::PgPool, is_removed: bool) -> Result<Vec<User>, sqlx::Error> {
    let users = User::select_many(pool, is_removed).await?;
    Ok(users)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT id, email, is_removed FROM users WHERE is_removed=$1"]
    pub async fn select_many_by_is_removed(
        pool: &sqlx::PgPool,
        is_removed: bool,
    ) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(
            User,
            "SELECT id, email, is_removed FROM users WHERE is_removed=$1",
            is_removed
        )
        .fetch_all(pool)
        .await?;
        Ok(object)
    }
}
```

</details>

## Insert

### Insert without returning

```rust
use sql_macros::SqlInsert;

#[derive(Debug, SqlInsert)]
#[table(name = "users")]
pub struct CreateUser {
    pub email: String,
}

pub async fn create(conn: &mut sqlx::PgConnection, data: &CreateUser) -> Result<u64, sqlx::Error> {
    let query_result = data.insert(conn).await?;
    Ok(query_result.rows_affected())
}
```

<details>
    <summary>View generated code</summary>

```rust
impl CreateUser {
    #[doc = "INSERT INTO users (email) VALUES ($1)"]
    pub async fn insert(
        &self,
        conn: &mut sqlx::PgConnection,
    ) -> Result<sqlx::any::AnyQueryResult, sqlx::Error> {
        let query_result = sqlx::query!("INSERT INTO users (email) VALUES ($1)", &self.email)
            .execute(&mut *conn)
            .await?;
        Ok(query_result.into())
    }
}
```

</details>

### Insert with returning

```rust
use sql_macros::SqlInsert;

#[derive(Debug, SqlInsert)]
#[table(name = "users", return_type = User)]
pub struct CreateUser {
    pub email: String,
}

pub async fn create(conn: &mut sqlx::PgConnection, data: &CreateUser) -> Result<User, sqlx::Error> {
    let user = data.insert(conn).await?;
    Ok(user)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl CreateUser {
    #[doc = "INSERT INTO users (email) VALUES ($1) RETURNING *"]
    pub async fn insert(&self, conn: &mut sqlx::PgConnection) -> Result<User, sqlx::Error> {
        let object = sqlx::query_as!(
            User,
            "INSERT INTO users (email) VALUES ($1) RETURNING *",
            &self.email
        )
        .fetch_one(&mut *conn)
        .await?;
        Ok(object)
    }
}

```

</details>

### Insert with returning fields

```rust
use sql_macros::SqlInsert;

#[derive(sqlx::FromRow)]
struct CreateUserResponse {
    pub id: i32,
}

#[derive(Debug, SqlInsert)]
#[table(name = "users", return_type = CreateUserResponse, return_fields = "id")]
pub struct CreateUser {
    pub email: String,
}

pub async fn create(conn: &mut sqlx::PgConnection, data: &CreateUser) -> Result<CreateUserResponse, sqlx::Error> {
    let user = data.insert(conn).await?;
    Ok(user)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl CreateUser {
    #[doc = "INSERT INTO users (email) VALUES ($1) RETURNING id"]
    pub async fn insert(&self, conn: &mut sqlx::PgConnection) -> Result<CreateUserResponse, sqlx::Error> {
        let object = sqlx::query_as!(
            CreateUserResponse,
            "INSERT INTO users (email) VALUES ($1) RETURNING id",
            &self.email
        )
        .fetch_one(&mut *conn)
        .await?;
        Ok(object)
    }
}

```

</details>

### Insert many

`SqlInsert` only inserts a single row. For inserting a batch of rows in one
round-trip, derive `SqlInsertMany` as well. Because the number of rows isn't
known at compile time, this can't use `sqlx::query!`/`query_as!` like the
other methods do — it's built at runtime with `sqlx::QueryBuilder` instead.

```rust
use sql_macros::SqlInsertMany;

#[derive(Debug, SqlInsertMany)]
#[table(name = "users", return_type = User)]
pub struct CreateUser {
    pub email: String,
}

pub async fn create_many(conn: &mut sqlx::PgConnection, data: &[CreateUser]) -> Result<Vec<User>, sqlx::Error> {
    let users = CreateUser::insert_many(data, conn).await?;
    Ok(users)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl CreateUser {
    #[doc = "INSERT INTO users (email) VALUES (...), (...), ... RETURNING *"]
    pub async fn insert_many(
        items: &[Self],
        conn: &mut sqlx::PgConnection,
    ) -> Result<Vec<User>, sqlx::Error> {
        if items.is_empty() {
            return Ok(Vec::new());
        }

        let mut builder = sqlx::QueryBuilder::new("INSERT INTO users (email) ");
        builder.push_values(items, |mut b, item| {
            b.push_bind(&item.email);
        });
        builder.push(" RETURNING ").push("*");

        let objects = builder
            .build_query_as::<User>()
            .fetch_all(&mut *conn)
            .await?;
        Ok(objects)
    }
}
```

</details>

Without `return_type`, `insert_many` returns `Result<sqlx::any::AnyQueryResult, sqlx::Error>` instead, same as `insert`.

### Upsert

Mark a field `#[table(upsert)]` to make it the `ON CONFLICT (...)` target for
`SqlInsert`/`SqlInsertMany`. Every other field becomes a
`DO UPDATE SET col = EXCLUDED.col` assignment (if every field were part of
the target, it falls back to `DO NOTHING`, since an empty `SET` is invalid
SQL).

```rust
use sql_macros::SqlInsert;

#[derive(Debug, SqlInsert)]
#[table(name = "users", return_type = User)]
pub struct UpsertUser {
    #[table(upsert)]
    pub email: String,
    pub is_active: bool,
}

pub async fn upsert(conn: &mut sqlx::PgConnection, data: &UpsertUser) -> Result<User, sqlx::Error> {
    let user = data.insert(conn).await?;
    Ok(user)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl UpsertUser {
    #[doc = "INSERT INTO users (email, is_active) VALUES ($1,$2) ON CONFLICT (email) DO UPDATE SET is_active=EXCLUDED.is_active RETURNING *"]
    pub async fn insert(&self, conn: &mut sqlx::PgConnection) -> Result<User, sqlx::Error> {
        let object = sqlx::query_as!(
            User,
            "INSERT INTO users (email, is_active) VALUES ($1,$2) ON CONFLICT (email) DO UPDATE SET is_active=EXCLUDED.is_active RETURNING *",
            &self.email as _,
            &self.is_active as _
        )
        .fetch_one(&mut *conn)
        .await?;
        Ok(object)
    }
}
```

</details>

`SqlInsertMany` supports the same `#[table(upsert)]` attribute; the
`ON CONFLICT` clause is appended once, after the batch `VALUES (...), (...),
...` list, and applies to every row.

## Update

### Update without returning

It just return query result (see `sqlx::any::AnyQueryResult`)

```rust
use sql_macros::SqlUpdate;

#[derive(SqlUpdate)]
#[table(name = "users")]
pub struct UpdateUser {
    #[table(update)]
    pub id: i32,
    pub email: String,
}

pub async fn update(conn: &mut sqlx::PgConnection, data: &UpdateUser) -> Result<u64, sqlx::Error> {
    let query_result = data.update_by_id(conn).await?;
    Ok(query_result.rows_affected())
}
```

<details>
    <summary>View generated code</summary>

```rust
impl UpdateUser {
    #[doc = "UPDATE users SET email=$1 WHERE id=$2"]
    pub async fn update_by_id(
        &self,
        conn: &mut sqlx::PgConnection,
    ) -> Result<sqlx::any::AnyQueryResult, sqlx::Error> {
        let result = sqlx::query!(
            "UPDATE users SET email=$1 WHERE id=$2",
           &self.email,
           &self.id
       )
       .execute(&mut *conn)
       .await?;
       Ok(result.into())
   }
}
```

</details>

### Update with returning type

```rust
use sql_macros::SqlUpdate;

#[derive(SqlUpdate)]
#[table(name = "users", return_type = User)]
pub struct UpdateUser {
    #[table(update)]
    pub id: i32,
    pub email: String,
}

pub async fn update(conn: &mut sqlx::PgConnection, data: &UpdateUser) -> Result<User, sqlx::Error> {
    let user = data.update_by_id(conn).await?;
    Ok(user)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl UpdateUser {
   #[doc = "UPDATE users SET email=$1 WHERE id=$2 RETURNING *"]
   pub async fn update_by_id(&self, conn: &mut sqlx::PgConnection) -> Result<User, sqlx::Error> {
       let object = sqlx::query_as!(
           User,
           "UPDATE users SET email=$1 WHERE id=$2 RETURNING *",
            &self.email,
            &self.id
        )
        .fetch_one(&mut *conn)
        .await?;
        Ok(object)
    }
}
```

</details>

### Update with returning fields

```rust
use sql_macros::SqlUpdate;

#[derive(sqlx::FromRow)]
struct UpdateUserResponse {
    pub id: i32,
}

#[derive(SqlUpdate)]
#[table(name = "users", return_type = UpdateUserResponse, return_fields = "id")]
pub struct UpdateUser {
    #[table(update)]
    pub id: i32,
    pub email: String,
}

pub async fn update(conn: &mut sqlx::PgConnection, data: &UpdateUser) -> Result<UpdateUserResponse, sqlx::Error> {
    let res = data.update_by_id(conn).await?;
    Ok(res)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl UpdateUser {
   #[doc = "UPDATE users SET email=$1 WHERE id=$2 RETURNING id"]
   pub async fn update_by_id(&self, conn: &mut sqlx::PgConnection) -> Result<UpdateUserResponse, sqlx::Error> {
       let object = sqlx::query_as!(
           UpdateUserResponse,
           "UPDATE users SET email=$1 WHERE id=$2 RETURNING id",
            &self.email,
            &self.id
        )
        .fetch_one(&mut *conn)
        .await?;
        Ok(object)
    }
}
```

</details>

### Update with special columns

```rust
use sql_macros::SqlUpdate;

#[derive(SqlUpdate)]
#[table(name = "users", spec_columns = "updated_at=NOW()")]
pub struct UpdateUser {
    #[table(update)]
    pub id: i32,
    pub email: String,
}

pub async fn update(conn: &mut sqlx::PgConnection, data: &UpdateUser) -> Result<u64, sqlx::Error> {
    let query_result = data.update_by_id(conn).await?;
    Ok(query_result.rows_affected())
}
```

<details>
  <summary>View generated code</summary>

```rust
impl UpdateUser {
   #[doc = "UPDATE users SET email=$1, updated_at=NOW() WHERE id=$2"]
   pub async fn update_by_id(
       &self,
       conn: &mut sqlx::PgConnection,
   ) -> Result<sqlx::any::AnyQueryResult, sqlx::Error> {
       let result = sqlx::query!(
            "UPDATE users SET email=$1, updated_at=NOW() WHERE id=$2",
            &self.email,
            &self.id
        )
        .execute(&mut *conn)
        .await?;
        Ok(result.into())
    }
}
```

</details>

## Delete

```rust
use sql_macros::SqlDelete;

#[derive(SqlDelete)]
pub struct User {
    #[table(delete)]
    pub id: i32,
}

async fn delete(conn: &mut sqlx::PgConnection, id: i32) -> Result<u64, sqlx::Error> {
    let result = User::delete_by_id(conn, id).await?;
    Ok(result.rows_affected())
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "DELETE FROM users WHERE id=$1"]
    pub async fn delete_by_id(
        conn: &mut sqlx::PgConnection,
        id: i32,
    ) -> Result<sqlx::any::AnyQueryResult, sqlx::Error> {
        let result = sqlx::query!("DELETE FROM users WHERE id=$1", id)
            .execute(&mut *conn)
            .await?;
        Ok(result.into())
    }
}
```

</details>

## Generate methods with many fields

```rust
use sql_macros::{SqlDelete, SqlSelect, SqlSelectMany, SqlUpdate};

#[derive(SqlSelect, SqlSelectMany, SqlDelete, SqlUpdate)]
#[table(select = get_active_user(is_active, is_removed))]
#[table(select_many = get_user_by_removed(is_active, is_removed))]
#[table(delete = delete_user(is_active, is_removed))]
#[table(update = update_by_email(email))]
pub struct User {
    pub id: i32,
    pub email: String,
    pub is_active: bool,
    pub is_removed: bool,
}
```

Works with select, select_many, delete, update.

For `update`, the listed fields (`email` above) become the `WHERE` filter
and every other field (`id`, `is_active`, `is_removed`) becomes a `SET`
column - same rule `update_by_<field>` follows via `#[table(update)]` on a
field, just parameterised so you can generate several differently-filtered
update methods on one struct:

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "UPDATE users SET id=$1, is_active=$2, is_removed=$3 WHERE email=$4"]
    pub async fn update_by_email(&self, conn: &mut sqlx::PgConnection) -> Result<sqlx::any::AnyQueryResult, sqlx::Error> {
        let result = sqlx::query!(
            "UPDATE users SET id=$1, is_active=$2, is_removed=$3 WHERE email=$4",
            &self.id,
            &self.is_active,
            &self.is_removed,
            &self.email
        )
        .execute(&mut *conn)
        .await?;
        Ok(result.into())
    }
}
```

</details>

## Comparison operators

A field's own single-field methods (`select_by_<field>`,
`select_many_by_<field>`, `delete_by_<field>`, `update_by_<field>`) default
to `=`. Add `op = "..."` to use something else:
`gt`/`lt`/`gte`/`lte` (`>`, `<`, `>=`, `<=`), `like`/`ilike` (`LIKE`/`ILIKE`
— `ilike` is Postgres's case-insensitive `LIKE`), or `in`/`not_in`
(`= ANY($n)`/`!= ALL($n)`, which also widen the generated parameter from
`FieldType` to `&[FieldType]`).

**This only applies to a field's own single-field methods** — a custom
multi-field method (`select = name(...)`) never reads it; those are always
`=`, `AND`-joined (see [Custom multi-field methods](#custom-multi-field-methods)
below for how to express something more complex there).

```rust
use sql_macros::SqlSelectMany;

#[derive(SqlSelectMany)]
pub struct User {
    pub email: String,
    #[table(select_many, op = "gt")]
    pub id: i32,
}

pub async fn get_newer_than(pool: &sqlx::PgPool, id: i32) -> Result<Vec<User>, sqlx::Error> {
    let users = User::select_many_by_id_gt(pool, id).await?;
    Ok(users)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT email, id FROM users WHERE id>$1"]
    pub async fn select_many_by_id_gt(pool: &sqlx::PgPool, id: i32) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(User, "SELECT email, id FROM users WHERE id>$1", id)
            .fetch_all(pool)
            .await?;
        Ok(object)
    }
}
```

</details>

Note the method name: any non-`eq` operator is suffixed onto the base name
(`select_many_by_id` -> `select_many_by_id_gt`), so the operator is visible
at the call site instead of being hidden behind a plain-looking name.

`op` also accepts a list — `op = ["gt", "lt"]` — generating one method
variant per operator, instead of one field forcing a single fixed
comparison everywhere a field can only have one meaning at a time:

```rust
#[derive(SqlSelectMany)]
pub struct User {
    pub email: String,
    #[table(select_many, op = ["gt", "lt"])]
    pub id: i32,
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT email, id FROM users WHERE id>$1"]
    pub async fn select_many_by_id_gt(pool: &sqlx::PgPool, id: i32) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(User, "SELECT email, id FROM users WHERE id>$1", id)
            .fetch_all(pool)
            .await?;
        Ok(object)
    }

    #[doc = "SELECT email, id FROM users WHERE id<$1"]
    pub async fn select_many_by_id_lt(pool: &sqlx::PgPool, id: i32) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(User, "SELECT email, id FROM users WHERE id<$1", id)
            .fetch_all(pool)
            .await?;
        Ok(object)
    }
}
```

</details>

This works the same way for `#[table(update)]` fields — `op = ["gt", "lt"]`
generates `update_by_age_gt` and `update_by_age_lt`, same shape as
`select_many_by_age_gt`/`select_many_by_age_lt`.

`op = "in"`/`"not_in"` change the parameter type, since they filter against
a list rather than a single value:

```rust
#[derive(SqlSelectMany)]
pub struct User {
    pub email: String,
    #[table(select_many, op = "in")]
    pub id: i32,
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT email, id FROM users WHERE id = ANY($1)"]
    pub async fn select_many_by_id_in(pool: &sqlx::PgPool, id: &[i32]) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(User, "SELECT email, id FROM users WHERE id = ANY($1)", id)
            .fetch_all(pool)
            .await?;
        Ok(object)
    }
}
```

</details>

## Custom multi-field methods

A custom multi-field method (`select = name(...)`, `select_many = name(...)`,
`update = name(...)`, `delete = name(...)`) is always `=`, `AND`-joined —
`#[table(op = "...")]` never applies here, on purpose: a field's own
comparison operator staying fixed to that field keeps a struct's attributes
readable at a glance, instead of the same field silently meaning something
different in every method that references it.

If you need something more than a plain `AND` of equalities — `OR`, `NOT`,
a different operator, anything — give the method a raw filter template
instead of a field list: a single quoted string where `$field` is *only*
the bound-value placeholder (numbered by first occurrence; the same field
referenced twice reuses one number). The column name, `=`, `OR`, `AND`,
`NOT`, parens, anything else in the string is your own SQL, passed through
unchanged.

```rust
use sql_macros::SqlSelectMany;

#[derive(SqlSelectMany)]
#[table(select_many = search_users(
    "email=$email OR (is_active=$is_active AND NOT is_removed=$is_removed)"
))]
pub struct User {
    pub id: i32,
    pub email: String,
    pub is_active: bool,
    pub is_removed: bool,
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT id, email, is_active, is_removed FROM users WHERE email=$1 OR (is_active=$2 AND NOT is_removed=$3)"]
    pub async fn search_users(
        pool: &sqlx::PgPool,
        email: String,
        is_active: bool,
        is_removed: bool,
    ) -> Result<Vec<User>, sqlx::Error> {
        let object = sqlx::query_as!(
            User,
            "SELECT id, email, is_active, is_removed FROM users WHERE email=$1 OR (is_active=$2 AND NOT is_removed=$3)",
            email,
            is_active,
            is_removed
        )
        .fetch_all(pool)
        .await?;
        Ok(object)
    }
}
```

</details>

This works the same way for `update = name("...")`, except the placeholders
are numbered *after* the `SET` columns, same as a plain field list would be.

## Select with enum

```rust
use sql_macros::SqlSelect;

#[derive(Debug, sqlx::Type)]
#[sqlx(type_name = "role", rename_all = "snake_case")]
pub enum Role {
    Admin,
    User,
    SuperAdmin,
}

#[derive(SqlSelect)]
pub struct User {
    #[table(select)]
    pub id: i32,
    pub email: String,
    #[table(as_type = "role!: Role")]
    pub role: Role,
}

pub async fn get_by_id(pool: &sqlx::PgPool, id: i32) -> Result<Option<User>, sqlx::Error> {
    let user = User::select_by_id(pool, id).await?;
    Ok(user)
}
```

<details>
    <summary>View generated code</summary>

```rust
impl User {
    #[doc = "SELECT id, email, role AS \"role!: Role\" FROM users WHERE id=$1"]
    pub async fn select_by_id(pool: &sqlx::PgPool, id: i32) -> Result<Option<User>, sqlx::Error> {
        let object = sqlx::query_as!(
            User,
            "SELECT id, email, role AS \"role!: Role\" FROM users WHERE id=$1",
            id
        )
        .fetch_optional(pool)
        .await?;
        Ok(object)
    }
}
```

</details>

## Attention

`return_type` without `return_fields` generates `RETURNING *`. That's a
problem if the return type has a column with a Postgres enum (or other
custom) type — `sqlx::query_as!` needs an `AS "col!: Type"` annotation to
decode it, and `*` can't carry one, since the macro only ever sees
`return_type` as a type name (a token), not the return type's own field
list — it has no way to know that field needs an override.

```rust
#[derive(Debug, sqlx::FromRow)]
pub struct User {
    pub id: i32,
    pub email: String,
    pub role: Role,
}

#[derive(Debug, SqlInsert)]
#[table(name = "users", return_type = User)]
pub struct CreateUser {
    pub email: String,
}
```

<details>
    <summary>Why this fails</summary>

```text
error: no built in mapping found for type role of column "role";
a type override may be required, see documentation for details
```

</details>

The fix: write the annotation yourself in `return_fields` — it's inserted
into the query as plain text, so anything valid after `RETURNING` works,
including a type override:

```rust
#[table(name = "users", return_type = User, return_fields = "id, email, role AS \"role!: Role\"")]
```