SQL/MX Glossary

Glossary

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Glossary-3

automatic SQL recompilation

automatic SQL recompilation. The SQL recompilation in memory of a program or SQL

statement invoked by the SQL executor at run time. Automatic recompilation occurs,

for example, when an SQL object definition has changed since the program’s last

explicit SQL compilation.

backout. To restore a file, database, or system to its previous condition by removing

changes. In transaction processing, to remove all the database changes performed by

a transaction that was aborted.

base table. A table that has physical existence: that is, a table stored in a file. Contrast with

Visual Query Planner. See also file.

base-table predicate. A predicate evaluated by the Data Access Manager on rows in the

base table.

binder. The second phase in the SQL compiler. This portion of the compile process takes

the syntactically correct query tree, translates logical names to physical names, and

performs semantic checks. The binder also expands views that are referenced in the

query, looks up metadata for SQL objects, and produces a semantically correct query

tree.

built-in function. A function defined by and part of the database that accepts arguments,

performs a specific operation, and returns one or more values. For example, the AVG

function is a built-in function in SQL/MX that returns the average of a set of numbers.

bulk move. The most efficient type of data transfer used by SQL/MP or SQL/MX. The SQL

executor selects a bulk move if one or more fields can be moved from a source (for

example, a SQL table in DP2 or a buffer in the master executor) to a target (for

example, an executor buffer or application host variable) by doing a string copy of all

the fields in one operation. The same is true for target-to-source (for example,

application host variable to executor buffer) data transfers. A bulk move is selected if

the source and target have the same data attributes (length, data type, scale, and so

on.) and if all the source fields are aligned the same way as the target. When a bulk

move is not selected, each source field is moved or converted to the target one field at

a time.

C/C++ preprocessor. See SQL preprocessor.

call-level interface (CLI). A library of function calls that supports SQL statements.

CASE expression. A conditional expression you can use to evaluate a set of conditions

and obtain a value based on the condition in the set that is true.