How to avoid unions in sql quries

Question

Hi All,
I have an sql statement in which I am using unions to get the data from two tables with different conditions. how can avoid UNIONs in  my query, which will increase performance. please suggest.
SQL Query is :
SELECT opt_url_path, locale
     FROM urlregistry
    WHERE master_assetid IN
             (SELECT c.id FROM content_c c, content_cd cc
               WHERE c.flextemplateid = cc.id AND cc.name = 'SoftwareDownload'
                     AND (c.PATH NOT LIKE '/auth%' AND c.PATH NOT LIKE '/gate%'))     
UNION
SELECT opt_url_path, locale
     FROM urlregistry
    WHERE master_assetid IN
             (SELECT c.id FROM content_c c, content_c_mungo cm
               WHERE c.id = cm.cs_ownerid AND cm.cs_attrid =
               (SELECT id FROM attribute WHERE name = 'Gated')
                 AND c.flextemplateid IN (SELECT id FROM content_cd WHERE name = 'Collateral')
                     AND cm.stringvalue = 'Yes'
                     AND (c.PATH NOT LIKE '/auth%'
                          AND c.PATH NOT LIKE '/gate%'))                              
UNION
SELECT PATH, locale
     FROM bloburlregistry
    WHERE master_assetid IN
             (SELECT c.id FROM content_c c, content_c_mungo cm
               WHERE c.id = cm.cs_ownerid AND cm.cs_attrid = (SELECT id FROM attribute WHERE name = 'Gated')
                     AND c.flextemplateid IN (SELECT id FROM content_cd WHERE name = 'Collateral')
                     AND cm.stringvalue = 'Yes'
                     AND (c.PATH NOT LIKE '/auth%'
                          AND c.PATH NOT LIKE '/gate%'))
Thank u.

Answer 1

To increase performance you need to reduce the I/O. So when ever i tune a SQL the first thing i look for is that. If i have a table used multiple times i try to remove it and solve the required problem by just scanning the table once. But do to that we need to have good understanding of the data and there relation between tables. But we don't know anything about yours. Said that i came up with this.
select opt_url_path
     , locale
  from urlregistry
where master_assetid
      IN
          select c.id
            from content_c c
            left
            join content_cd cc
              on c.flextemplateid = cc.id
             and (cc.name = 'SoftwareDownload' or cc.name = 'Collateral')
            left
            join content_c_mungo cm
              on c.id = cm.cs_ownerid
             and cm.cs_attrid =
                     SELECT id
                       FROM attribute
                      WHERE name = 'Gated'
             and cm.stringvalue = 'Yes'
           where c.PATH NOT LIKE '/auth%'
             and c.PATH NOT LIKE '/gate%'
             and (
                    cc.flextemplateid is not null or
                    cm.cs_owner_id    is not null
union
select PATH
     , locale
  from bloburlregistry
where master_assetid IN
          select c.id
            from content_c c
               , content_c_mungo cm
           where c.id = cm.cs_ownerid
             and cm.cs_attrid =
                     SELECT id
                       FROM attribute
                      WHERE name = 'Gated'
             and c.flextemplateid IN
                     SELECT id
                       FROM content_cd
                      WHERE name = 'Collateral'
             and cm.stringvalue = 'Yes'
             and c.PATH NOT LIKE '/auth%'
             and c.PATH NOT LIKE '/gate%'
This is a untested code. You can give this a try and see if it gives the expected output and also if the performance improves.