Oracle SQL Extensions - Glossary

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Conditional Compilation enables you to selectively include code depending on the values of the conditions evaluated during compilation. For example, conditional compilation enables you to determine which PL/SQL features in a PL/SQL application are used for specific database releases. The latest PL/SQL features in an application can be run on a new database release while at the same time those features can be conditionalized so that the same application is compatible with a previous database release. Conditional compilation is also useful when you want to execute debugging procedures in a development environment, but want to turn off the debugging routines in a production environment.
Access method
The course of action required to retrieve the data. For example, retrieving data by using an index is an access method.
Array
A type of object used to store repeating sets of a single datatype. The datatype can be either a regular datatype such as NUMBER or an object type that you define. An array has a pre-defined limit to the number of rows it contains.
Block
Each tablespace is subdivided into increments called blocks. The exact size for a block depends on the operating system in which the database resides. One block is the smallest increment of space the database can allocate to a table.
Check constraint
A condition that is required for every row in the table.
Column constraint
Constraints that apply to one column.
Constraint
A constraint is a database rule that you define within the database to enforce certain conditions regarding the data that is stored in the database tables.
Correlated sub-query
A sub-query in which part of the sub-query refers back to data in the outer query.
Data dictionary views
Oracle views that display meta-data.
Data Manipulation Language (DML)
SQL commands that modify data stored in tables. These commands insert, update, or delete rows of data.
Datafile
The physical files that Oracle uses to store data. A datafile is a contiguous segment of a disk drive.
Dynamic list
A list of values created by adding a sub-query to a query. This kind of list is dynamic because the list of values always reflects the current values in the database.
Foreign key
A column or list of columns in one table that contain data that references the primary key of another table.
Glossary
To access all the items in the course glossary, click the Show All Terms button, below.
Group function
A group function is a predefined way to combine rows of information together and display summarized data. A common group function is the SUM function, which adds values into a total sum.
Hierarchical query
A form of query that retrieves data according to a hierarchy defined with a recursive relationship on a table. A parent/child list is produced that lists all the "children" items under their "parent" item.
Inner join
A join where only the rows of one table that are matched with the rows of the other table are used in the query results.
Instance
One row in an object table.
JDBC
Java Database Connectivity. A set of standards defining a standard protocol and syntax in Java applications or applets to interact with any relational database.
Left outer join
An outer join in which the left table in the Fromclause may contain rows that don't match with a row in the right table.
Meta-data
Information (data) about database structures. For example, the meta-data about a table includes its name, its column names, and the tablespace in which it resides.
Nested table
A type of object used to store repeating sets of a single datatype. The datatype can be either a regular datatype such as NUMBER or an object type that you define. A nested table can have an unlimited number of rows.
Object table
An object table is a table whose row is defined as one instance of an object type. A relational table, by comparison, is a table whose row is defined as one or more columns with predefined datatypes (number, varchar2, and so on).
Object type
This is the definition method for creating an object-oriented object. It is similar to a datatype.
Object-oriented design
A design that allows you to not only define what data you can store in your database, you also define a set of actions (methods) associated with the data.
ODBC
Open Database Connectivity. A set of standards that define communication protocol and syntax to be used when interacting with any relational database.
Outer join
A special variation of the kind of query that combines two or more tables into a single query. In an outer join, rows in one table that contain no match with the other table are included in the result set returned from the query.
Primary key
One or more columns that define a unique row in a table. A table can contain only one primary key.
Pseudocolumn
A pseudocolumn is data that Oracle makes available to you when it executes SQL commands. These are created for convenience. For example, the Oracle user name that is executing the SQL is contained in the pseudocolumn called USER.
Reference
The equivalent of a foreign key within an object-oriented design.
Right outer join
An outer join in which the right table in the Fromclause may contain rows that don't match with a row in the left table.
Schema
All the tables, views, and other objects created by a single Oracle user. The schema has the same name as the creating user, such as the SCOTT schema.
Table constraint
Constraints that apply to more than one column.
Tablespace
Logical storage space within the Oracle database. Each tablespace is mapped to one or more physical data files. Each tablespace stores one or more tables, indexes, or other objects created within the database. A table is assigned to a single tablespace when the table iscreated except where you have created a partitioned table.
Unique key
A second primary key in a table. A table can contain more than one unique key.
Wildcard
A symbol that is used for pattern matching when using the LIKE operator. For example, % and _ are the two wildcards used in Oracle. The % wildcard can match any number of characters. The _ wildcard can match any single character.