Learn XQuery

Joins

Relational databases are designed to optimize joins, so DataDirect XQuery® leverages the database when an XQuery join involves SQL data. Performing all the joins in the database results in a dramatic performance gain, because DataDirect XQuery simply uses the SQL engine in your database.

Example 4. Join Pushdown

XQuery

for $u in collection('USERS')/USERS
for $h in collection('HOLDINGS')/HOLDINGS
where $u/USERID = $h/USERID
return <holding name="{$u/LASTNAME}">{$h/SHARES/text()}</holding>

Generated SQL

SELECT ALL
 nrm5."LASTNAME" AS RACOL1,
 nrm9."SHARES" AS RACOL2
FROM
 "PEPPINO"."USERS" nrm5,
 "PEPPINO"."HOLDINGS" nrm9
WHERE
 nrm5."USERID" = nrm9."USERID" AND
 LENGTH(nrm5."USERID") = LENGTH(nrm9."USERID")

Next: "Sorting Data" Prev: "Quantifiers"

Try DataDirect XQuery® Free!

Put the power, scalability, and performance of DataDirect XQuery® to work for you today! Our free trial lets you see for yourself how easy it is to build data integration applications that access relational, EDI, and other file formats as XML!

Download DataDirect XQuery® today!

Online Video Tutorials!

Our easy-to-follow online video tutorials are a great way to get acquainted with the many features of DataDirect XQuery®.

And if you like what you see, download a free copy today and try DataDirect XQuery® for yourself!

Feeds

Multimedia

Newsletter