Figure out references

script/sql/create/19.reactions.sql

@@ -22,14 +22,20 @@ create table reactions_pipe_bulk
 , value numeric not null
 );
 
+-- delete when delete pipe
+
 create table reactions_pipe_wall
 (
   pipe  varchar(32) primary key references pipes(id) not null
 , value numeric not null
 );
 
+-- delete when delete pipe
+
 create table reactions_tank
 (
   tank  varchar(32) primary key references tanks(id) not null
 , value numeric not null
 );
+
+-- delete when delete tank