SQL/MX Glossary

Glossary
HP NonStop SQL/MX Glossary—523732-002
Glossary-18
leaf operator
leaf operator. An operator in an operator tree that has no children. An example of a leaf
operator in an operator tree is the scan node. The EXPLAIN row for a relational leaf
operator will have NULL value for the left and the right child column.
left hybrid hash join. A left hybrid hash join returns an unmatched outer row even when it
does not find a match in the inner table. Null values are supplied for the missing inner
rows. This operation differs from a hybrid hash join only when it does not find a match
in the inner table. See also hybrid hash join.
left join on. A type of join that joins rows that satisfy the search condition in the ON clause
of a join operation, plus rows from the left table that do not satisfy the search condition.
left merge join. A portion of an execution plan that involves a merge join. This operation
differs from a merge join only when it does not find a match in the inner table. When no
match is found, the left row is still returned, and the data from the right table is set to
null. See also sort merge join.
left nested join. A portion of an execution plan that involves a nested join. This operation
sends each outer (left) row to the inner (right) child. The right child finds all the
matches for a row and returns all the matches. If an outer row finds no matches in the
inner table, the outer row is returned and nulls are supplied for inner table values. See
also nested join.
literal. A constant in an expression or statement. An SQL literal can be a datetime,
INTERVAL, numeric, or character string literal.
live upgrade. The ability to replace the program file of a running process with an identically
named file. The HP NonStop operating system supports live upgrades for applications
that can be loaded directly from the HP NonStop Open System Services (OSS) or
NonStop operating system command line, but not Java applications, which are
interpreted by a Java Virtual Machine (JVM).
local autonomy. The principle that users of a node in a network can perform operations on
objects on that node even when other nodes are not available and also manage nodes
independently.
local transaction. A transaction that is processed by a single transaction manager on a
single node. Contrast with distributed transaction.
location-independent ANSI name. An SQL/MX catalog, schema, or database object name
that is subject to visibility rules. ANSI name lookup resolves a name starting with the
system schema tables on the local node. The name does not include an expand node
name and cannot be guaranteed to unambiguously identify a database object in an
Expand network.
lock. A mechanism that coordinates concurrent access to the same data. See also
exclusive lock, lock duration, lock granularity, and shared lock.
lock duration. The period of time during which a lock is held.