databases

aggregate functions (COUNT, MIN, MAX, and AVG) special functions that perform arithmetic computations over a set of rows. Usually used in conjunction with a GROUP BY clause to group the output of aggregate computations by one or more attribute rows that match a given condition.            

ANSI SQL data types Basic types include; NUMBER, NUMERIC, INTEGER, CHAR, VARCHAR, and DATE. Support is different in each RDBMS.   Microsoft Access Equivalent ANSI SQL Data Types         

AREA Named section of permanent storage space that is reserved to store the database. Used in DB2.            

byte 8 binary bits.   Wikipedia         

candidate key Minimal superkey. Key that does not contain a subset of attributes that is itself a superkey.            

closure Property of relational operators that permits the end use of relational algebra operators on existing tables (relations) to produce new relations.            

column Each database table column represents an attribute. Each column has a distinct name.            

column list Represents one or more column names separated by commas. May also include computed columns, aliases, and aggregate functions.            

composite entity (aka: bridge entity, associative entity) Designed to transform a M:N relationship into two 1:M relationships. Composite entity's primary key comprises at least the primary keys of the entities that it connects.            

composite key Multiple-attribute key.            

correlated subquery Subquery that executes once for each row in the outer query.            

Data Manipulation Commands (DML) Allow you to add, modify, and delete rows from tables. Basic commands are; SELECT, INSERT, UPDATE, DELETE, COMMIT, and, ROLLBACK.             

database A collection of data.   Wikipedia         

Database Description (DBD) One of the OSPF protocol messages.            

Database Handle (DBH) ($dbh)            

dependent Value of an attribute that is determined by another attribute.            

determination The role of a key. (A determines B)            

domain Used to organize and describe an attribute's set of possible values in data modeling.            

gigabyte (GB) 1 billion bytes.   Wikipedia         

HAVING clause The HAVING clause is used to restrict the output of a GROUP BY query by applying a conditional criteria to the grouped rows.            

IBM Db2 DB2(tm) and Db2(tm) refer to database-server products developed by IBM. These products all support the relational model, but in recent years, some products have been extended to support object-relational features and non-relational structures like JSON and XML. Successor to the 1980s-introducded DB2. Announced in 2017.  Website  Wikipedia       

IN Equality operator. Can be used in place of INTERSECT if IN is not supported by the DBMS.            

INSERT SQL command used in databases to add new rows to tables.            

MINUS Relational set operator. SQL command that combines rows from two queries and returns only the rows that appear in the first set but not in the second.            

query (aka: Information retrieval) A request for information. A question.   Wikipedia (Query)  Wikipedia (Information Retrieval)       

simple attribute Attribute that cannot be subdivided.            

SQL commands Can be divided into two overall categories: data definition language (DDL) and data manipulation language (DML) commands.            

subquery Query linked to another query.   Wikipedia         

TO_NUMBER Oracle function used to convert a character string into a number. Digits are represented by “9”.            

Updatable View Can be used to update attributes in the base tables that are used in the view.            

WHERE SQL clause that narrows query results. Can be used with SELECT, UPDATE, and DELETE statements to restrict rows affected by the DDL command.    Wikipedia