Crossed foreign keys in SQL

Question

Hi,

I am trying to have 2 tables with crossed foreign keys, but I am not allowed to reference a table that doesn't exist when I am creating them. Any way of creating tables like this for mysql, something like declare both tables at the same time or delay evaluation of foreign keys?

Error is 1005: Can't create table blocks.frm (errno 150) on a mysql 5.0

SQL:

create table if not exists blocks( 
    id int unsigned not null auto_increment, 
    title varchar(100),
    defaultpage int unsigned not null, 
    foreign key(defaultpage) references pages(pageID), 
    primary key(id)) engine=innodb;

create table if not exists pages( 
    pageID int unsigned not null auto_increment, 
    title varchar(50) not null, 
    content blob,  
    blockid int unsigned not null, 
    foreign key(blockid) references block(id), 
    primary key(pageID) ) engine=innodb;

What is the proper way to solve the problem?

Answer 1

Bringing cletus's answer (which is perfectly correct) to the code...

create table if not exists pages( 
    pageID int unsigned not null auto_increment, 
    title varchar(50) not null, 
    content blob,  
    blockid int unsigned not null, 
    primary key(pageID) ) engine=innodb;

create table if not exists blocks( 
    id int unsigned not null auto_increment, 
    title varchar(100),
    defaultpage int unsigned not null, 
    foreign key(defaultpage) references pages(pageID), 
    primary key(id)) engine=innodb;

alter table pages add constraint fk_pages_blockid foreign key (blockid) references blocks (id);

Answer 2

You can delay foreign key checking until the tables are created:

SET FOREIGN_KEY_CHECKS = 0;
CREATE TABLE ...;
SET FOREIGN_KEY_CHECKS = 1;