accessor ID
An accessor ID designates a user. This is a user's ID, not a schema's authorization ID.
alternate key
An alternate key is any key which must be unique within the table, but which is not also the primary key.
See foreign key, key, and primary key.
authorization ID
Every table, view, plan, and synonym is contained in a schema and every schema is identified by an authorization ID. A fully qualified object's name includes the authorization ID of the schema containing the object.
bind
Binding is the process of preparing a program for execution. Language compilers and linkage editors prepare source programs for execution in a target environment such as CICS. The SQL Preprocessor and plan generator prepare the data sublanguage portions of a source program for execution by the SQL Manager.
CA Datacom/DB delays some decisions which impact the method used to execute an SQL statement until execution time if information required to make the best decision is not available until execution time. This technique is called "phased binding." In effect, the binding process is performed in discrete phases and one of those phases does not occur until execution time.
clause
In SQL, a distinct part of a statement introduced by a keyword, such as WHERE.
column
The vertical component of a table. A column describes an indivisible unit of data in a table. A column has a name and a particular data type, for example, character or integer.
column constraints
A constraint (see constraints) whose definition controls a single column in a base table, specified within the column definition syntax of a CREATE TABLE statement or within an ALTER TABLE statement.
column functions
Summary operators in SQL that permit users to perform operations on the value of a column. The functions include average, count, maximum, minimum and sum.
Also see scalar functions.
commit
The process that allows CA Datacom/DB data, which has been changed by an application or user, to be referenced by other applications or users. When a commit occurs, locks are freed so that other applications can reference the just-committed data. When data has been committed, a new commit point is established. Committed data cannot be rolled back.
commit point
A point in time when data is considered to be consistent.
compound statement
A compound statement is the building block from which SQL Procedures are mostly composed.
Also see SQL Procedure.
constraints
A restriction that is attached to a table in order to regulate data values or properties or relationships between values. Specific constraint types include:
An SQL integrity constraint cannot reference a partitioned table, nor a partition of a partitioned table. That is to say, constraints and partitioned tables are mutually exclusive.
cursor
A named control structure used by an application program to point to a row. The position of the row is within some ordered set of rows. The cursor is used to retrieve rows from the set, possibly making updates or deletions.
SQL's FETCH, positioned UPDATE, and positioned DELETE statements support the concept of positioned operations. The row of a table to be operated on is identified by the positioning information maintained with the cursor control structure.
cursor processing
Cursor processing isolates a cursor from changes made by other statements in an application program while the cursor is open.
cursor stability
The isolation level that provides a high degree of concurrency. With cursor stability, a unit of recovery holds locks only on the current row of each of its cursors.
See isolation level.
data type
An attribute of columns, literals and host variables. The data types are halfword integer (SMALLINT), fullword integer (INTEGER), floating point (FLOAT, REAL, DOUBLE PRECISION), packed decimal (DECIMAL), zoned decimal (NUMERIC), and fixed-length character string (CHARACTER).
dynamic SQL
Dynamic SQL uses variables in the host language to contain the SQL source. The SQL statements are then dynamically prepared and executed within an application program as it runs and can change one or more times during the execution of that program.
embedded SQL
SQL statements that are embedded in a host language program and are prepared during the program preparation process before the program is executed. After it is prepared, the statement itself does not change, although values of host variables specified within the statement could change.
External Procedure
An External Procedure is one whose body of logic is written in some host programming language outside SQL.
Also see SQL Procedure and host program.
foreign key
Foreign keys define relationships between tables. The column(s) of a foreign key in one table are related to the primary key of some table. That related primary key may not be defined on the same table as the foreign key.
Every foreign key is related to a primary key. A primary key may be related to zero, one, or many foreign keys.
Each foreign key defines a referential integrity constraint. Every foreign key value (the column values of the foreign key's columns from a single row of the table) must exactly match a primary key value of the foreign key's related primary key. When a foreign key value exists which does not match any primary key value of its related primary key, the referential integrity constraint is violated.
See alternate key, key, and primary key.
host language
A programming language, such as COBOL, in which SQL language statements are embedded.
host program
A program written in a host language, such as COBOL, that contains embedded SQL statements.
Also see host language.
host variable
A host language variable referenced by embedded SQL statements.
index
Tables are often accessed by the data values they contain in one or more columns. To make such accesses efficient, the tables can be indexed by one or more columns.
Such an index supports quick access to the table's rows by their data value content. A given table can support multiple indexes. CA Datacom/DB automatically maintains the index as the table's content changes.
An index is a performance-only consideration to the SQL user. The presence or absence of an index does not enhance or restrict the logical operations supported for a table.
CA Datacom/DB also supports a special type of index to control the physical placement of rows to enhance performance. This "clustering index" is automatically created by the system when this space management option is selected. See your Database Administrator for more information about space management options.
index-only processing
Index-only processing retrieves data, when possible, from the index only, eliminating the cost of accessing the actual row in the data area.
inner join
See join.
isolation level
The degree to which a unit of recovery is isolated from the uncommitted changes of other units of work.
At the lowest level, no locks are acquired for rows accessed "read-only." This allows you to access rows that have been updated by another unit of recovery even though the changes have not been committed.
See cursor stability and repeatable read.
join
A relational operation that allows retrieval of data from two or more tables based on a relational comparison of column values. That is, a join is a query used to return rows that consist of columns selected from more than one table. A new table therefore results from a join. There are different kinds of joins. Inner joins eliminate from the resulting table the combined rows that do not satisfy evaluation against the join predicates. Therefore, with inner joins if no matching row is found, no rows are returned. Outer joins (also see left outer joins) preserve the rows an inner join would discard by returning those rows with nulls substituted for each column of one of the tables.
key
The term "key" in CA Datacom/DB predates SQL. Its original meaning was the same as the definition given for the term "index." To conform with industry standards and to reduce confusion, the meaning of the term "key" in CA Datacom/DB is changed to conform with broader industry usage.
The term "index" is reserved for referencing physical addressing mechanisms which impact performance.
The term "key" is reserved for referencing logical concepts which impact functionality.
In general, a key is one or more columns of a table. The logical significance of a key depends on its type.
See alternate key, foreign key, and primary key.
left outer join
An outer join (see join) in which the column values coming from the outer (left) table are preserved, and non-matching rows from the inner (right) table have their result-column values represented as NULLs.
memory guard
The SQL Memory Guard is an SQL memory monitoring function, normally used only if requested by CA Support.
object
Anything that can be created or manipulated with SQL, for example, tables or views.
outer join
See join.
partitioned tables
Partitioned tables allow you to store the rows of a single table in multiple data areas. Table partitioning helps provide enhanced data availability.
With regard to the effects of table partitioning on SQL, ALTER, CREATE, and DROP statements may not be issued against a table which is partitioned nor against a partition. An SQL integrity constraint cannot reference a partitioned table, nor a partition of a partitioned table. That is to say, constraints and partitioned tables are mutually exclusive. For more information about defining and using partitioned tables, see the CA Datacom/DB Database and System Administration Guide.
plan
The control structure produced during the bind process and used by CA Datacom/DB to process SQL statements encountered during application execution. The plan contains information about SQL statements. Each program containing embedded SQL statements must have a plan before being executed.
predicate
A syntactic unit of a search condition that can be evaluated to give a truth value of true, false, or unknown.
primary key
A table's primary key provides a guaranteed method of addressing each row of the table by using the data value of all columns participating in the primary key. This requires that the primary key value of each row be unique for the table. A given table has, at most, one primary key. A relational base table has exactly one primary key.
See alternate key, foreign key, and key.
privilege
A privilege defines what kind of access (SELECT, INSERT, UPDATE, DELETE) is authorized for a particular resource. You must be granted the necessary privilege to execute specific commands, or to grant privileges to other users. The CA Datacom/DB Security Facility must be installed before privileges can be defined.
procedures
Procedures are user-written programs that execute inside the Multi-User Facility as a separate subtask. They can be coded to perform almost any task and generally contain SQL statements. They can be executed explicitly using a CALL or EXECUTE PROCEDURE statement or can be triggered implicitly by a user-specified database management system event.
See triggers.
referential integrity constraints
A foreign key constraint. That is to say, each foreign key defines a referential integrity constraint. See foreign key.
relational database
A database perceived by the user as a collection of tables.
repeatable read
The isolation level that provides maximum protection from other executing application programs. When a program executes with repeatable read protection, rows referenced by the program cannot be changed by other programs until the program reaches a commit point.
See isolation level.
Resource Recovery Services (RRS)
Resource Recovery Services (RRS) is a protocol that protects the integrity of resources maintained by an application that runs on multiple resource managers. This protection is provided by using a two-phase commit protocol during runtime, and by querying and reacting to the RRS log during restart. With this feature, CA Datacom/DB interacts with RRS as a resource manager.
For further information on RRS, see the CA Datacom/DB Database and System Administration Guide.
result table
A derived table which consists of rows selected for an application program.
rollback
The process of restoring data changed by SQL statements to the state at its last commit point.
row
The horizontal component of a table. A row consists of a sequence of values, one for each column of the table. Rows are the unit of insertion and deletion, whereas, individual columns can be updated. A table can exist without any rows.
RRS
See Resource Recovery Services (RRS).
scalar functions
Produce a single value from another value. Expressed in the form of a function name followed by a list of arguments in parentheses.
Also see column functions.
schema
Associated with each authorization ID is one and only one schema. A schema contains the tables, views, plans, and synonyms which are qualified by its authorization ID.
search condition
A criterion for selecting rows from a table. A search condition consists of one or more predicates.
SQL
SQL is a database sub-language which can be used to define, manipulate, and control data in a databases.
SQL Memory Guard
See memory guard.
SQL Procedure
SQL procedure are those whose body of logic written is in the SQL language.
Also see External Procedure and compound statement.
status tables
SQL status tables provide information about the current status of the SQL subsystem. SQL status tables are located in the dynamic system tables database.
See the CA Datacom/DB System Tables Reference Guide for detailed information.
subquery
A SELECT statement within the WHERE or HAVING clause of another SQL statement. A nested SQL statement.
synonym
To allow short names to be used in a schema, a synonym can be assigned for an object's full name. The full name of the object is required to reference an object defined in a schema owned by one authorization ID from a schema owned by a different authorization ID. That full name includes the authorization ID of the schema which defines the object.
Within the schema containing the synonym, the full name and the assigned synonym are equivalent. Every SQL statement which is subject to interpretation in the context of an authorization ID can make use of synonyms as an alternative to the full name of an object.
table
A table is a named data object consisting of a specific number of columns and a variable number of unordered rows. Each row in a specific table must have the same number of columns. Although the order of columns in a table is fixed, there is no conceptual significant to the order of columns. Likewise, the order of rows is not specified in a table's definition and contains no conceptual significance.
table constraints
A constraint whose definition may control the properties of or relationships between more than one column. See constraints.
table partitioning
See partitioned tables.
triggers
Defines a triggering event which causes a triggered action to occur. A triggering event may be an INSERT, UPDATE, or DELETE and may be further restricted to trigger only for certain columns and column data values. The triggered action may be a procedure call.
See procedures.
union
An SQL operation that combines the results of two SELECT statements. Union is often used to merge lists of values obtained from several tables.
unit of recovery
The data and control information needed to enable CA Datacom/DB to back out or reapply all of an application's changes to recoverable resources since the last commit point.
unit of work
A unit of work is made up of one or more units of recovery. In a batch environment, a unit of work corresponds to the execution of an application program. Within that program, there may be many units of recovery as COMMIT or ROLLBACK statements are executed.
value
Data stored at the intersection of a row and column in a table.
view
An alternative representation of data from one or more tables. A view is a derived table which can include all or some of the columns contained in the table or tables on which it is defined.
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