PGSQL 视图 FULL JOIN 可以有多少?
PQSQL中创建视图如下:
SELECT contacts_im.im, contacts_im.date, contacts_im.class AS iclass, contacts_im.fields, contacts_im.upuser, contacts.createdate, contacts.updatedate, contacts.id, contacts."from", contacts.name, contacts."user", contacts.class, contacts_email.host,contacts_address."zip" ...
FROM contacts
FULL JOIN contacts_im ON contacts_im.class = contacts.id
FULL JOIN contacts_email ON contacts_email.class = contacts.id
FULL JOIN contacts_address ON contacts_address.class = contacts.id
...
FULL JOIN
请问这么多的FULL JOIN可以吗?效率如何?
然后SELECT如何调用视图,还有如何排序,是创建视图时排序还是SELECT的时候,怎么写?
然后视图可以WHERE吗?比如WHERE contacts.id = 1?在视图中WHERE还是SELECT时WHERE?