Imagine you have datas with n:m relationship which is resolved to three tables,
like in the attached database.
Go to "Create Query in SQL view..." and create a query with an INNER JOIN, like
query "querymitJoinSQLansicht" in the example. Save it. If you look into the
content.xml, you see the command 
SELECT "de"."BEGRIFF", "en"."ITEM" FROM "de" INNER JOIN "translate" ON "de"."ID"
= "translate"."DE_ID" INNER JOIN "en" ON "en"."ID" = "translate"."EN_ID"

Now use context menu "Edit" for that query. It opens in Design mode. Move the
table-icons a little bit but don't alter the query itself. Save it. I have done
it with the query "kopiezumbearbeiten" in the example. Now look into content.xml
again. You see the command
SELECT "de"."BEGRIFF", "en"."ITEM" FROM "de" "de", "translate" "translate", "en"
"en" WHERE ( "de"."ID" = "translate"."DE_ID" AND "en"."ID" = "translate"."EN_ID

OOo has silently changed your command. That is bad, because, for example for an
Access database connected via ADO, the WHERE version is extreme slow compared
with the INNER JOIN version and makes your query unusable, if the database
contains not only a few records.