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WHERE clause
PQL recognizes the WHERE clause the same way
SQL does. Use the WHERE clause to restrict
or filter your search. For example:
SELECT systemname||' '||name,size,freespace FROM /network/device/wmi/win32_logicaldisk WHERE drivetype = 3
This query searches for disk drive capacity and freespace on all systems, but is limited by only one type of drive.
Instances of a sub-tree — or records, if you're still thinking in
tables — are selected using the WHERE clause, as with SQL.
Once you've targeted a sub-tree in the FROM clause, the
WHERE clause uses children of the target as attributes
in the selection.
Depending on your database, this query finds results similar to this:
row systemname || || name KYOTO C: size 12889010176 Bytes freespace 2686287872 Bytes row systemname || || name KYOTO D: size 237044310016 Bytes freespace 102629593088 Bytes row systemname || || name CHIBA C: size 18161414144 Bytes freespace 796418048 Bytes row systemname || || name CHIBA E: size 163921571840 Bytes freespace 106091302912 Bytes ...
See path-scoped projection
for an explanation of how to limit the query output.
See path-scoped predicate
for ways to write the WHERE clause with more elegance.
