SQL/MX Glossary

Glossary
HP NonStop SQL/MX Glossary—523732-002
Glossary-17
Java Database Connectivity (JDBC)
Java Database Connectivity (JDBC). The Java standard for access to relational
databases such as SQL/MP or SQL/MX.
Java method. A function defined in a Java class.
Java object. An instantiation of a Java class.
Java Virtual Machine (JVM). Software that loads, links, verifies, and interprets Java
bytecode.
join. A database operation that combines two or more tables into a single logical table so
that data can be selected from all the tables at once. Types of joins include natural
inner (or natural), natural left, natural right, join on, left join on, right join on, merge join,
left merge join, soft merge join, nested join, left nested join, hash join, hybrid hash join,
left hybrid hash join, and simple hash join.
join on. A type of join that joins only rows that satisfy the search condition in the ON clause.
join predicate. A predicate that identifies and compares columns in a join operation.
K
key predicate. A predicate that specifies begin-key conditions, end-key conditions, or both
to narrow the range of searching an SQL table. Such conditions reduce the number of
rows fetched; this reduction of physical I/O operations improves performance.
key prefix. A leading (leftmost) contiguous set of columns in the key.
key-sequenced file. A file in which each new record is stored in sequence by a primary or
clustering key. See also primary key and clustering key. Contrast with entry-sequenced
file.
key-sequenced table. A table stored in a key-sequenced file, where the storage key can be
defined by the user, by both the user and the system (SYSKEY), or by the SYSKEY
alone. You cannot update columns in a user-defined clustering or primary key.
Columns can be added to the table, rows can be updated or deleted, and variable-
length values can be shortened or lengthened. Contrast with entry-sequenced table.
L
label. See file label.
language manager. See SQL/MX language manager.
late name resolution. A comparison made by SQL/MX to determine whether a new table
name specified at run time by a host variable or a DEFINE is the same as a previous
table name. When a table name changes in a query, SQL/MX can recompile the query
or use its previous access plan depending on the outcome of a similarity check.