query_hql.pot

hibernate-distribution-3.3.1.GA-dist.zip源码

msgstr ""

#. Tag: programlisting
#: query_hql.xml:861
#, no-c-format
msgid ""
      "<![CDATA[select cat.id, (select max(kit.weight) from cat.kitten kit)\n"
      "from Cat as cat]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:863
#, no-c-format
msgid "Note that HQL subqueries may occur only in the select or where clauses."
msgstr ""

#. Tag: para
#: query_hql.xml:867
#, no-c-format
msgid "Note that subqueries can also utilize <literal>row value constructor</literal> syntax. See <xref linkend=\"queryhql-tuple\"/> for more details."
msgstr ""

#. Tag: title
#: query_hql.xml:875
#, no-c-format
msgid "HQL examples"
msgstr ""

#. Tag: para
#: query_hql.xml:877
#, no-c-format
msgid "Hibernate queries can be quite powerful and complex. In fact, the power of the query language is one of Hibernate's main selling points. Here are some example queries very similar to queries that I used on a recent project. Note that most queries you will write are much simpler than these!"
msgstr ""

#. Tag: para
#: query_hql.xml:883
#, no-c-format
msgid "The following query returns the order id, number of items and total value of the order for all unpaid orders for a particular customer and given minimum total value, ordering the results by total value. In determining the prices, it uses the current catalog. The resulting SQL query, against the <literal>ORDER</literal>, <literal>ORDER_LINE</literal>, <literal>PRODUCT</literal>, <literal>CATALOG</literal> and <literal>PRICE</literal> tables has four inner joins and an (uncorrelated) subselect."
msgstr ""

#. Tag: programlisting
#: query_hql.xml:892
#, no-c-format
msgid ""
      "<![CDATA[select order.id, sum(price.amount), count(item)\n"
      "from Order as order\n"
      "    join order.lineItems as item\n"
      "    join item.product as product,\n"
      "    Catalog as catalog\n"
      "    join catalog.prices as price\n"
      "where order.paid = false\n"
      "    and order.customer = :customer\n"
      "    and price.product = product\n"
      "    and catalog.effectiveDate < sysdate\n"
      "    and catalog.effectiveDate >= all (\n"
      "        select cat.effectiveDate\n"
      "        from Catalog as cat\n"
      "        where cat.effectiveDate < sysdate\n"
      "    )\n"
      "group by order\n"
      "having sum(price.amount) > :minAmount\n"
      "order by sum(price.amount) desc]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:894
#, no-c-format
msgid "What a monster! Actually, in real life, I'm not very keen on subqueries, so my query was really more like this:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:899
#, no-c-format
msgid ""
      "<![CDATA[select order.id, sum(price.amount), count(item)\n"
      "from Order as order\n"
      "    join order.lineItems as item\n"
      "    join item.product as product,\n"
      "    Catalog as catalog\n"
      "    join catalog.prices as price\n"
      "where order.paid = false\n"
      "    and order.customer = :customer\n"
      "    and price.product = product\n"
      "    and catalog = :currentCatalog\n"
      "group by order\n"
      "having sum(price.amount) > :minAmount\n"
      "order by sum(price.amount) desc]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:901
#, no-c-format
msgid "The next query counts the number of payments in each status, excluding all payments in the <literal>AWAITING_APPROVAL</literal> status where the most recent status change was made by the current user. It translates to an SQL query with two inner joins and a correlated subselect against the <literal>PAYMENT</literal>, <literal>PAYMENT_STATUS</literal> and <literal>PAYMENT_STATUS_CHANGE</literal> tables."
msgstr ""

#. Tag: programlisting
#: query_hql.xml:909
#, no-c-format
msgid ""
      "<![CDATA[select count(payment), status.name\n"
      "from Payment as payment\n"
      "    join payment.currentStatus as status\n"
      "    join payment.statusChanges as statusChange\n"
      "where payment.status.name <> PaymentStatus.AWAITING_APPROVAL\n"
      "    or (\n"
      "        statusChange.timeStamp = (\n"
      "            select max(change.timeStamp)\n"
      "            from PaymentStatusChange change\n"
      "            where change.payment = payment\n"
      "        )\n"
      "        and statusChange.user <> :currentUser\n"
      "    )\n"
      "group by status.name, status.sortOrder\n"
      "order by status.sortOrder]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:911
#, no-c-format
msgid "If I would have mapped the <literal>statusChanges</literal> collection as a list, instead of a set, the query would have been much simpler to write."
msgstr ""

#. Tag: programlisting
#: query_hql.xml:916
#, no-c-format
msgid ""
      "<![CDATA[select count(payment), status.name\n"
      "from Payment as payment\n"
      "    join payment.currentStatus as status\n"
      "where payment.status.name <> PaymentStatus.AWAITING_APPROVAL\n"
      "    or payment.statusChanges[ maxIndex(payment.statusChanges) ].user <> :currentUser\n"
      "group by status.name, status.sortOrder\n"
      "order by status.sortOrder]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:918
#, no-c-format
msgid "The next query uses the MS SQL Server <literal>isNull()</literal> function to return all the accounts and unpaid payments for the organization to which the current user belongs. It translates to an SQL query with three inner joins, an outer join and a subselect against the <literal>ACCOUNT</literal>, <literal>PAYMENT</literal>, <literal>PAYMENT_STATUS</literal>, <literal>ACCOUNT_TYPE</literal>, <literal>ORGANIZATION</literal> and <literal>ORG_USER</literal> tables."
msgstr ""

#. Tag: programlisting
#: query_hql.xml:927
#, no-c-format
msgid ""
      "<![CDATA[select account, payment\n"
      "from Account as account\n"
      "    left outer join account.payments as payment\n"
      "where :currentUser in elements(account.holder.users)\n"
      "    and PaymentStatus.UNPAID = isNull(payment.currentStatus.name, PaymentStatus.UNPAID)\n"
      "order by account.type.sortOrder, account.accountNumber, payment.dueDate]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:929
#, no-c-format
msgid "For some databases, we would need to do away with the (correlated) subselect."
msgstr ""

#. Tag: programlisting
#: query_hql.xml:933
#, no-c-format
msgid ""
      "<![CDATA[select account, payment\n"
      "from Account as account\n"
      "    join account.holder.users as user\n"
      "    left outer join account.payments as payment\n"
      "where :currentUser = user\n"
      "    and PaymentStatus.UNPAID = isNull(payment.currentStatus.name, PaymentStatus.UNPAID)\n"
      "order by account.type.sortOrder, account.accountNumber, payment.dueDate]]>"
msgstr ""

#. Tag: title
#: query_hql.xml:938
#, no-c-format
msgid "Bulk update and delete"
msgstr ""

#. Tag: para
#: query_hql.xml:940
#, no-c-format
msgid "HQL now supports <literal>update</literal>, <literal>delete</literal> and <literal>insert ... select ...</literal> statements. See <xref linkend=\"batch-direct\"/> for details."
msgstr ""

#. Tag: title
#: query_hql.xml:948
#, no-c-format
msgid "Tips &amp; Tricks"
msgstr ""

#. Tag: para
#: query_hql.xml:950
#, no-c-format
msgid "You can count the number of query results without actually returning them:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:954
#, no-c-format
msgid "<![CDATA[( (Integer) session.createQuery(\"select count(*) from ....\").iterate().next() ).intValue()]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:956
#, no-c-format
msgid "To order a result by the size of a collection, use the following query:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:960
#, no-c-format
msgid ""
      "<![CDATA[select usr.id, usr.name\n"
      "from User as usr\n"
      "    left join usr.messages as msg\n"
      "group by usr.id, usr.name\n"
      "order by count(msg)]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:962
#, no-c-format
msgid "If your database supports subselects, you can place a condition upon selection size in the where clause of your query:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:967
#, no-c-format
msgid "<![CDATA[from User usr where size(usr.messages) >= 1]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:969
#, no-c-format
msgid "If your database doesn't support subselects, use the following query:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:973
#, no-c-format
msgid ""
      "<![CDATA[select usr.id, usr.name\n"
      "from User usr.name\n"
      "    join usr.messages msg\n"
      "group by usr.id, usr.name\n"
      "having count(msg) >= 1]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:975
#, no-c-format
msgid "As this solution can't return a <literal>User</literal> with zero messages because of the inner join, the following form is also useful:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:980
#, no-c-format
msgid ""
      "<![CDATA[select usr.id, usr.name\n"
      "from User as usr\n"
      "    left join usr.messages as msg\n"
      "group by usr.id, usr.name\n"
      "having count(msg) = 0]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:982
#, no-c-format
msgid "Properties of a JavaBean can be bound to named query parameters:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:986
#, no-c-format
msgid ""
      "<![CDATA[Query q = s.createQuery(\"from foo Foo as foo where foo.name=:name and foo.size=:size\");\n"
      "q.setProperties(fooBean); // fooBean has getName() and getSize()\n"
      "List foos = q.list();]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:988
#, no-c-format
msgid "Collections are pageable by using the <literal>Query</literal> interface with a filter:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:992
#, no-c-format
msgid ""
      "<![CDATA[Query q = s.createFilter( collection, \"\" ); // the trivial filter\n"
      "q.setMaxResults(PAGE_SIZE);\n"
      "q.setFirstResult(PAGE_SIZE * pageNumber);\n"
      "List page = q.list();]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:994
#, no-c-format
msgid "Collection elements may be ordered or grouped using a query filter:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:998
#, no-c-format
msgid ""
      "<![CDATA[Collection orderedCollection = s.filter( collection, \"order by this.amount\" );\n"
      "Collection counts = s.filter( collection, \"select this.type, count(this) group by this.type\" );]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1000
#, no-c-format
msgid "You can find the size of a collection without initializing it:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1004
#, no-c-format
msgid "<![CDATA[( (Integer) session.createQuery(\"select count(*) from ....\").iterate().next() ).intValue();]]>"
msgstr ""

#. Tag: title
#: query_hql.xml:1009
#, no-c-format
msgid "Components"
msgstr ""

#. Tag: para
#: query_hql.xml:1011
#, no-c-format
msgid "Components might be used in just about every way that simple value types can be used in HQL queries. They can appear in the <literal>select</literal> clause:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1016 query_hql.xml:1062
#, no-c-format
msgid "<![CDATA[select p.name from Person p]]>"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1017
#, no-c-format
msgid "<![CDATA[select p.name.first from Person p]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1019
#, no-c-format
msgid "where the Person's name property is a component. Components can also be used in the <literal>where</literal> clause:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1024
#, no-c-format
msgid "<![CDATA[from Person p where p.name = :name]]>"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1025
#, no-c-format
msgid "<![CDATA[from Person p where p.name.first = :firstName]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1027
#, no-c-format
msgid "Components can also be used in the <literal>order by</literal> clause:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1031
#, no-c-format
msgid "<![CDATA[from Person p order by p.name]]>"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1032
#, no-c-format
msgid "<![CDATA[from Person p order by p.name.first]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1034
#, no-c-format
msgid "Another common use of components is in <link linkend=\"queryhql-tuple\">row value constructors</link>."
msgstr ""

#. Tag: title
#: query_hql.xml:1040
#, no-c-format
msgid "Row value constructor syntax"
msgstr ""

#. Tag: para
#: query_hql.xml:1042
#, no-c-format
msgid "HQL supports the use of ANSI SQL <literal>row value constructor</literal> syntax (sometimes called <literal>tuple</literal> syntax), even though the underlying database may not support that notion. Here we are generally referring to multi-valued comparisons, typically associated with components. Consider an entity Person which defines a name component:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1049
#, no-c-format
msgid "<![CDATA[from Person p where p.name.first='John' and p.name.last='Jingleheimer-Schmidt']]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1051
#, no-c-format
msgid "That's valid syntax, although a little verbose. It be nice to make this a bit more concise and use <literal>row value constructor</literal> syntax:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1056
#, no-c-format
msgid "<![CDATA[from Person p where p.name=('John', 'Jingleheimer-Schmidt')]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1058
#, no-c-format
msgid "It can also be useful to specify this in the <literal>select</literal> clause:"
msgstr ""

#. Tag: para
#: query_hql.xml:1064
#, no-c-format
msgid "Another time using <literal>row value constructor</literal> syntax can be beneficial is when using subqueries needing to compare against multiple values:"
msgstr ""

#. Tag: programlisting
#: query_hql.xml:1069
#, no-c-format
msgid ""
      "<![CDATA[from Cat as cat\n"
      "where not ( cat.name, cat.color ) in (\n"
      "    select cat.name, cat.color from DomesticCat cat\n"
      ")]]>"
msgstr ""

#. Tag: para
#: query_hql.xml:1071
#, no-c-format
msgid "One thing to consider when deciding if you want to use this syntax is that the query will be dependent upon the ordering of the component sub-properties in the metadata."
msgstr ""