Databases
StackOverflow2013
Postsdbo
POHow to know the on delete action of references table while adding foreign keys
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow to know the on delete action of references table while adding foreign keys
    primarykey
    data
    text
    <p>I am working on building new stuff on database that is already built by someone else and with little documentation. I need add a new table with many to many reference to a table already existing. </p> <p>The following is the table already existing wp_posts:</p> <pre><code>+-----------------------+---------------------+------+-----+---------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------------+---------------------+------+-----+---------------------+----------------+ | ID | bigint(20) unsigned | NO | PRI | NULL | auto_increment | | post_author | bigint(20) unsigned | NO | MUL | 0 | | | post_date | datetime | NO | | 0000-00-00 00:00:00 | | | guid | varchar(255) | NO | | | | | menu_order | int(11) | NO | | 0 | | | post_type | varchar(20) | NO | MUL | post | | | post_mime_type | varchar(100) | NO | | | | | comment_count | bigint(20) | NO | | 0 | | | legacy_id | int(11) | YES | | NULL | | +-----------------------+---------------------+------+-----+---------------------+----------------+ </code></pre> <p>I need to create a table tag and tag_posts_reference which helps me for many to many reference tables. The Tag table is wp_tags:</p> <pre><code>+-------+---------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+---------------------+------+-----+---------+----------------+ | id | bigint(20) unsigned | NO | PRI | NULL | auto_increment | | tag | varchar(255) | YES | | NULL | | +-------+---------------------+------+-----+---------+----------------+ </code></pre> <p>I am having trouble in creating the table wp_tags_posts. Its is giving me the following error:</p> <pre><code> mysql&gt; create table wp_posts_tags( id bigint(20) unsigned auto_increment, post_id bigint(20) unsigned not null, tag_id bigint(20) unsigned not null, primary key(id), index(post_id), foreign key(post_id) references wp_posts(id) on Update cascade on delete restrict, index(tag_id), foreign key(tag_id) references wp_tags(id)) ENGINE = INNODB; ERROR 1005 (HY000): Can't create table 'openexhibits_dev.wp_posts_tags' (errno: 150) </code></pre> <p>I think there is some delete on cascade actions I am supposed to add. I added few and tried by trial and error but none of them work. Is there a way I can find delete cascade action that I am supposed to use while creating the foreign key reference? Is there any command like dec table_name which can show me those actions? I tried on delete no action and on delete set null etc but I dont want to do something by trial and error blindly especially while dealing with relations between tables. Can anyone help me? Thank you very much. </p>
    singulars
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PTQuestion
    1. USMaddy
    1. USMaddy
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow to know the on delete action of references table while adding foreign keys
      1. This table or related slice is empty.
      1. VTUpMod
    1. COWhat storage engine are the tables using? Foreign key constraints only work on InnoDB tables.
      singulars
      1. POHow to know the on delete action of references table while adding foreign keys
      1. USeggyal
    2. COI am using InnoDB. Sorry for not adding it there.
      singulars
      1. POHow to know the on delete action of references table while adding foreign keys
      1. USMaddy
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload