umbraco-clear-recycle-bin.sql

--deletes in Document
--at this point all associated media files are deleted
delete from umbracoDomains where id in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsDocument where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
 
--deletes in Content
delete from cmsPropertyData where contentNodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsPreviewXml where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsContentVersion where ContentId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsContentXml where NodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
 
--deletes in CMSNode
delete from umbracoRelation where parentId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoRelation where childId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsTask where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoUser2NodeNotify where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsTagRelationship where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoUser2NodePermission where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsContent where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoNode where path like '%-20%' and id!=-20;

Seems like the umbracoUser2NodePermission table got renamed in a recent Umbraco version, so line 18 should now be:

DELETE FROM umbracoUserGroup2NodePermission WHERE nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);

See here: https://our.umbraco.com/forum/using-umbraco-and-getting-started/87181-unable-to-empty-recycle-bin#comment-300165

I can confirm this script, together with Nicholas's addition, is valid for Umbraco version 7.15.4 assembly: 1.0.7381.11453.

I have a couple of issues..
When I get to delete from umbracoNode where path like '%-20%' and id!=-20;
when there are nodes in the recycle bin with access restrictions the FK constraints on nodeId, loginNodeId and noAccessNodeId prevent deletes.
I also get an error about parentId on node SameTable constraint stops delete ??

Any work around?

Please try the following scripts if you haven't found the work around yet, works well with v8.13.1

--deletes in Document
--at this point all associated media files are deleted
delete from umbracoDomain where id in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoDocument where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);

--deletes in Content
delete from umbracoPropertyData where versionId in (select id from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20));
delete from umbracoDocumentVersion where id in (select id from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20));
delete from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsContentNu where NodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);

--deletes in CMSNode
delete from umbracoRelation where parentId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoRelation where childId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoUser2NodeNotify where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsTagRelationship where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoUserGroup2NodePermission where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoContent where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoContentSchedule where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20)
delete from umbracoRedirectUrl where contentKey in (select uniqueId from umbracoNode where path like '%-20%' and id!=-20)
delete from umbracoNode where path like '%-20%' and id!=-20;

Updated for Umbraco 11.4.2 (to include VersionCulture tables):

--deletes in Document
--at this point all associated media files are deleted
delete from umbracoDomain where id in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoDocument where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoDocumentVersion where id in (select id from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20));
delete from umbracoDocumentCultureVariation where nodeid in (select id from umbracoNode where path like '%-20%' and id!=-20);

--deletes in Content
delete from umbracoPropertyData where versionId in (select id from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20));
delete from umbracoContentVersionCultureVariation where versionid in (select id from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20));
delete from umbracoContentVersion where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsContentNu where NodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);

--deletes in CMSNode
delete from umbracoRelation where parentId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoRelation where childId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoUser2NodeNotify where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from cmsTagRelationship where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoUserGroup2NodePermission where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoContent where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20);
delete from umbracoContentSchedule where nodeId in (select id from umbracoNode where path like '%-20%' and id!=-20)
delete from umbracoRedirectUrl where contentKey in (select uniqueId from umbracoNode where path like '%-20%' and id!=-20)
delete from umbracoNode where path like '%-20%' and id!=-20;