macro_rules! allow_tables_to_appear_in_same_query { ($left_mod:ident, $($right_mod:ident),+ $(,)*) => { ... }; ($last_table:ident,) => { ... }; () => { ... }; }
Expand description
Allow two or more tables which are otherwise unrelated to be used together in a query.
This macro must be invoked any time two tables need to appear in the same query either because they are being joined together, or because one appears in a subselect. When this macro is invoked with more than 2 tables, every combination of those tables will be allowed to appear together.
If you are using diesel print-schema
, an invocation of
this macro will be generated for you for all tables in your schema.
ยงExample
// This would be required to do `users.inner_join(posts.inner_join(comments))`
allow_tables_to_appear_in_same_query!(comments, posts, users);
table! {
comments {
id -> Integer,
post_id -> Integer,
body -> VarChar,
}
}
table! {
posts {
id -> Integer,
user_id -> Integer,
title -> VarChar,
}
}
table! {
users {
id -> Integer,
name -> VarChar,
}
}
When more than two tables are passed, the relevant code is generated for every combination of those tables. This code would be equivalent to the previous example.
allow_tables_to_appear_in_same_query!(comments, posts);
allow_tables_to_appear_in_same_query!(comments, users);
allow_tables_to_appear_in_same_query!(posts, users);