Skip to main content
Version: 0.10.x 🚧

Custom Joins

You can use the join method to construct complex join select queries. It takes any RelationDef defined in entity files, and you can define relation with the belongs_to method as well. Join type is specified using JoinType such as inner join, left join and right join.

use sea_orm::{JoinType, RelationTrait};
use sea_query::Expr;

assert_eq!(
cake::Entity::find()
.column_as(filling::Column::Id.count(), "count")
.column_as(
Expr::tbl(Alias::new("fruit_alias"), fruit::Column::Name).into_simple_expr(),
"fruit_name"
)
// construct `RelationDef` on the fly
.join_rev(
JoinType::InnerJoin,
cake_filling::Entity::belongs_to(cake::Entity)
.from(cake_filling::Column::CakeId)
.to(cake::Column::Id)
.into()
)
// reuse a `Relation` from existing Entity
.join(JoinType::InnerJoin, cake_filling::Relation::Filling.def())
// join with table alias and custom on condition
.join_as(
JoinType::LeftJoin,
cake::Relation::Fruit
.def()
.on_condition(|_left, right| {
Expr::tbl(right, fruit::Column::Name)
.like("%tropical%")
.into_condition()
}),
Alias::new("fruit_alias")
)
.group_by(cake::Column::Id)
.having(filling::Column::Id.count().equals(Expr::value(2)))
.build(DbBackend::MySql)
.to_string(),
[
"SELECT `cake`.`id`, `cake`.`name`, COUNT(`filling`.`id`) AS `count`, `fruit_alias`.`name` AS `fruit_name` FROM `cake`",
"INNER JOIN `cake_filling` ON `cake_filling`.`cake_id` = `cake`.`id`",
"INNER JOIN `filling` ON `cake_filling`.`filling_id` = `filling`.`id`",
"LEFT JOIN `fruit` AS `fruit_alias` ON `cake`.`id` = `fruit_alias`.`cake_id` AND `fruit_alias`.`name` LIKE '%tropical%'",
"GROUP BY `cake`.`id`",
"HAVING COUNT(`filling`.`id`) = 2",
]
.join(" ")
);

You can use a custom struct derived from the FromQueryResult trait to handle the result of such complex query. See here for details.