Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I'd go with firstly setting up the myGroup and person tables.</p> <p>Secondly, I'd set up a myGroupGroup table with columns myGroupId, parentMyGroupId. This will allow you to relate group rows to child group rows i.e. "this group has these groups within it". If a group has no rows in this table then it has no child groups within it.</p> <p>Thirdly, I'd set up a personGroup table with columns personId, myGroupId. This will allow you to relate person rows to a given group. If a group has no rows in this table then it has no persons within it.</p> <pre><code>CREATE TABLE person( id INT UNSIGNED PRIMARY KEY, name VARCHAR(100) ) ENGINE=innodb; CREATE TABLE myGroup( id INT UNSIGNED PRIMARY KEY, groupName VARCHAR(100) ) ENGINE=innodb; -- Holds groups within groups CREATE TABLE myGroupGroup( id INT UNSIGNED PRIMARY KEY, myGroupId INT UNSIGNED, parentMyGroupId INT UNSIGNED DEFAULT NULL, CONSTRAINT `fk_myGroupGroup_group1` FOREIGN KEY (`parentMyGroupId`) REFERENCES `myGroup` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `fk_myGroupGroup_group2` FOREIGN KEY (`myGroupId`) REFERENCES `myGroup` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=innodb; -- Holds persons within a group CREATE TABLE personGroup( id INT, personId int UNSIGNED NOT NULL, myGroupId int UNSIGNED NOT NULL, CONSTRAINT `fk_personGroup_group1` FOREIGN KEY (`myGroupId`) REFERENCES `myGroup` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `fk_personGroup_person1` FOREIGN KEY (`personId`) REFERENCES `person` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=innodb; </code></pre> <p>I've tweaked your SQL a bit:</p> <p>1) Replaced <code>TYPE</code> with <code>ENGINE</code></p> <p>2) Replaced table name <code>group</code> with <code>myGroup</code> (<code>GROUP</code> is a <a href="http://dev.mysql.com/doc/refman/5.1/en/reserved-words.html" rel="nofollow">reserved word</a>)</p> <p>Good luck!</p>
    singulars
    1. This table or related slice is empty.
    1. PONesting of groups or elements
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USTom Mac
    1. USTom Mac
    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. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. CODear Tom, Thank you for you comments and explanations. Regarding your solution, I think there is an issue (that is solved on the solution presented by ypercube): I might need that some group have BOTH person AND Group members. In any case I much appreciate your answer. Regards.
      singulars
      1. PO
      1. USacombo
    2. COto cater for this I intended there to be a row in the personGroup table (for the persons in the group) e.g. groupId=1, personId=3 (so groupId 1 has person 3 in it). In the myGroup table a parent child relationship to indicate the groups within the group. So id=2, name='group2' and parentGroupId=1 to show that group 2 is part of group 1. You could move the self-referencing foreign key from the myGroup table into a myGroupGroup table or something similar if you wanted to make it clearer. Hope that helps!
      singulars
      1. PO
      1. USTom Mac
    3. COIn fact - I prefer the myGroupGroup idea (I think it is clearer). I have modified my answer accordingly. Hope it makes sense
      singulars
      1. PO
      1. USTom Mac
 

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