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WGU C170 SQL DATA MANIPULATION
DOMAIN EVALUATION: TERMINAL
PROFICIENCY TEST VERSION A 2026.
◍ Associative Entity. Ans: Also known as composite entity ◍ Bridge Entity. Ans: Another name for a composite entity ◍ candidate key. Ans: A minimal superkey; that is, a key that does not contain a subset of attributes that is itself a superkey. ◍ closure. Ans: A property of relational operators that permits the use of relational algebra operators on existing tables (relations) to produce new relations. ◍ composite entity. Ans: An entity designed to transform an M:N relationship into two 1:M relationships. The composite entity's primary key comprises at least the primary keys of the entities that it connects. Also known as a bridge entity. See also linking table. ◍ composite key. Ans: A multiple attribute key ◍ dependent. Ans: An attribute whose value is determined by another attribute.
◍ determination. Ans: The role of a key. In the context of a database table, the statement "A determines B" indicates that knowing the value of attribute A means that the value of attribute B can be looked up. ◍ DIFFERENCE. Ans: In relational algebra, an operator used to yield all rows from one table that are not found in another union- compatible table. ◍ DIVIDE. Ans: In relational algebra, an operator that answers queries about one set of data being associated with all values of data in another set of data. ◍ domain. Ans: In data modeling, the construct used to organize and describe an attributes set of possible values. ◍ entity integrity. Ans: The property of a relational table that guarantees each entity has a unique value in a primary key and that the key has no null values. ◍ equijoin. Ans: A join operator that links tables based on an equality condition that compares specified columns of the tables. ◍ flags. Ans: Special codes implemented by designers to trigger a required response, alert end users to specified conditions, or encode
◍ inner join. Ans: A join operation in which only rows that meet a given criterion are selected. The join criterion can be an equality condition (natural join or equijoin) or an inequality condition (theta join). The inner join is the most commonly used type of join. Contrast with outer join. ◍ INTERSECT. Ans: In relational algebra, an operator used to yield only the rows that are common to two union-compatible tables. ◍ JOIN. Ans: In relational algebra, a type of operator used to yield rows from two tables based on criteria. There are many types of joins, such as natural join, theta join, equijoin, and outer join. ◍ join column(s). Ans: Columns that join two tables. The join columns generally share similar values. ◍ key. Ans: one or more attributes that determine other attributes ◍ key attribute. Ans: The attributes that form a primary key ◍ left outer join. Ans: A join that includes all of the rows from the first table in the query and only those records from the second table that match the join field in the first table. ◍ linking table. Ans: In the relational model, a table that implements an M:M relationship.
◍ natural join. Ans: A relational operation that yields a new table composed of only the rows with common values in their common attribute(s). ◍ null. Ans: The absence of an attribute value. Note that a null is not a blank. ◍ outer join. Ans: Returns a set of records that include what an inner join would return but also includes other rows for which no corresponding match is found in the other table. ◍ predicate logic. Ans: Used extensively in mathematics to provide a framework in which an assertion (statement of fact) can be verified as either true or false. ◍ primary key (PK). Ans: In the relational model, an identifier composed of one or more attributes that uniquely identifies a row. Also, a candidate key selected as a unique entity identifier. ◍ prime attribute. Ans: A key attribute; that is, an attribute that is part of a key or is the whole key. ◍ PRODUCT. Ans: In relational algebra, an operator used to yield all possible pairs of rows from two tables. Also known as the Cartesian Product.
◍ set theory. Ans: A part of mathematical science that deals with sets, or groups of things, and is used as the basis for data manipulation in the relational model. ◍ superkey. Ans: An attribute or attributes that uniquely identify each entity in a table. ◍ system catalog. Ans: A detailed system data dictionary that describes all objects in a database. ◍ theta join. Ans: A join operator that links tables using an inequality comparison operator (<, >, <=, >=) in the join condition. ◍ UNION. Ans: In relational algebra, an operator used to merge two tables into a new table, dropping the duplicate rows. Tables must first be union-compatible. ◍ union-compatible. Ans: Two or more tables that have the same number of columns and the corresponding columns have compatible domains. ◍ unique index. Ans: An index in which the index key can have only one associated pointer value (row). ◍ binary relationship. Ans: An ER term for an association (relationship) between two entities. For example, PROFESSOR teaches CLASS.
◍ cardinality. Ans: A property that assigns a specific value to connectivity and expresses the range of allowed entity occurrences associated with a single occurrence of the related entity. ◍ composite attribute. Ans: An attribute that can be further subdivided to yield additional attributes. ◍ derived attribute. Ans: An attribute that does not physically exist within the entity and is derived via an algorithm. ◍ existence-dependent. Ans: A property of an entity whose existence depends on one or more other entities. ◍ existence independent. Ans: A property of an entity that can exist apart from one or more related entities. Such a table must be created first when referencing an existence-dependent table. ◍ identifiers. Ans: One or more attributes that uniquely identify each entity instance. ◍ iterative process. Ans: A process based on repetition of steps and procedures. ◍ mandatory participation. Ans: A relationship in which one entity occurrence must have a corresponding occurrence in another entity.
◍ relationship degree. Ans: The number of entities or participants associated with a relationship. A relationship degree can be unary, binary, ternary, or higher. ◍ required attribute. Ans: In ER modeling, an attribute that must have a value. In other words, it cannot be left empty. ◍ simple attribute. Ans: An attribute that cannot be subdivided into meaningful components. Compare to composite attribute. ◍ single-valued attribute. Ans: An attribute that can have only one value. ◍ strong (identifying) relationship. Ans: A relationship that occurs when two entities are existence-dependent; from a database design perspective, this relationship exists whenever the primary key of the related entity contains the primary key of the parent entity. ◍ strong entity. Ans: An entity that is existence-independent, that is, it can exist apart from all of its related entities. Also called a regular entity. ◍ ternary relationship. Ans: An ER term used to describe an association (relationship) between three entities. For example, a DOCTOR prescribes a DRUG for a PATIENT.
◍ unary relationship. Ans: An ER term used to describe an association within an entity. For example, an EMPLOYEE might manage another EMPLOYEE. ◍ weak entity. Ans: An entity that displays existence dependence and inherits the primary key of its parent entity. For example, a DEPENDENT requires the existence of an EMPLOYEE. ◍ weak relationship. Ans: A relationship in which the primary key of the related entity does not contain a primary key component of the parent entity. ◍ alias. Ans: An alternative name for a column or table in a SQL statement. ◍ ALTER TABLE. Ans: The SQL command used to make changes to table structure. When the command is followed by a keyword (ADD or MODIFY), it adds a column or changes column characteristics. ◍ AND. Ans: The SQL logical operator used to link multiple conditional expressions in a WHERE or HAVING clause. It requires that all conditional expressions evaluate to true. ◍ authentication. Ans: The process through which a DBMS verifies that only registered users can access the database.
◍ DELETE. Ans: A SQL command that allows data rows to be deleted from a table. ◍ DISTINCT. Ans: A SQL clause that produces only a list of values that are different from one another. ◍ DROP INDEX. Ans: The SQL command used to delete an index ◍ DROP TABLE. Ans: A SQL command that permanently deletes a table and its data. ◍ EXISTS. Ans: In SQL, a comparison operator that checks whether a subquery returns any rows. ◍ FROM. Ans: A SQL clause that specifies the table or tables from which data is to be retrieved. ◍ GROUP BY. Ans: A SQL clause used to create frequency distributions when combined with any of the aggregate functions in a SELECT statement. ◍ HAVING. Ans: A clause applied to the output of a GROUP BY operation to restrict selected rows. ◍ IN. Ans: In SQL, a comparison operator used to check whether a value is among a list of specified values.
◍ inner query. Ans: A query that is embedded or nested inside another query. Also known as a nested query or a subquery. ◍ INSERT. Ans: The SQL command used to add rows to a table ◍ International Organization for Standardization (ISO). Ans: An organization formed to develop standards for diverse network systems. ◍ IS NULL. Ans: In SQL, a comparison operator used to check whether an attribute has a value. ◍ LIKE. Ans: In SQL, a comparison operator used to check whether an attribute's text value matches a specified string pattern. ◍ MAX. Ans: A SQL aggregate function that yields the maximum attribute value in a given column. ◍ message. Ans: In the OO data model, the name of a method sent to an object in order to perform an action. A message triggers the object's behavior. ◍ method. Ans: In the object-oriented data model, a named set of instructions to perform an action. Methods represent real-world actions, and are invoked through messages.
◍ ROLLBACK. Ans: A SQL command that restores the database table contents to the condition that existed after the last COMMIT statement. ◍ subquery. Ans: A query that is embedded (or nested) inside another query. Also known as a nested query or an inner query. ◍ SUM. Ans: A SQL aggregate function that yields the sum of all values for a given column or expression. ◍ UPDATE. Ans: A SQL command that allows attribute values to be changed in one or more rows of a table. ◍ WHERE. Ans: A SQL clause that adds conditional restrictions to a SELECT statement that limit the rows returned by the query. ◍ base tables. Ans: The table on which a view is based. ◍ batch update routine. Ans: A routine that pools transactions into a single group to update a master table in a single operation. ◍ correlated subquery. Ans: A subquery that executes once for each row in the outer query.
◍ CREATE VIEW. Ans: A SQL command that creates a logical, "virtual" table. The view can be treated as a real table. ◍ cross join. Ans: A join that performs a relational product (or Cartesian product) of two tables. ◍ set-oriented. Ans: Dealing with or related to sets, or groups of things. ◍ updatable view. Ans: A view that can update attributes in base tables that are used in the view. ◍ view. Ans: A virtual table based on SELECT query that is saved as an object in the database. ◍ access plan. Ans: A set of instructions generated at application compilation time that is created and managed by a DBMS. The access plan predetermines how an application's query will access the database at run time. ◍ algorithms. Ans: A process or set of operations in a calculation. ◍ automatic query optimization. Ans: A method by which a DBMS finds the most efficient access path for the execution of a query.
of disk blocks used, maximum and average row length, number of columns in each row, and number of distinct values in each column. Such statistics provide a snapshot of database characteristics. ◍ DBMS performance tuning. Ans: Activities to ensure that clients' requests are addressed as quickly as possible while making optimum use of existing resources. ◍ dynamic query optimization. Ans: The process of determining the SQL access strategy at run time, using the most up-to-date information about the database. ◍ dynamic statistical generation mode. Ans: In a DBMS, the capability to automatically evaluate and update the database access statistics after each data access operation. ◍ extents. Ans: In a DBMS environment, refers to the ability of data files to expand in size automatically using predefined increments. ◍ file group. Ans: See table space. ◍ hash index. Ans: An index based on an ordered list of hash values. ◍ input/output (I/O) request. Ans: A low-level data access operation that reads or writes data to and from computer devices.
◍ manual query optimization. Ans: An operation mode that requires the end user or programmer to define the access path for the execution of a query. ◍ manual statistical generation mode. Ans: A mode of generating statistical data access information for query optimization. In this mode, the DBA must periodically run a routine to generate the data access statistics—for example, running the RUNSTAT command in an IBM DB2 database. ◍ procedure cache. Ans: See SQL cache. ◍ query optimizer. Ans: A DBMS process that analyzes SQL queries and finds the most efficient way to access the data. The query optimizer generates the access or execution plan for the query. ◍ query processing bottleneck. Ans: In query optimization, a delay introduced in the processing of an I/O operation that causes the overall system to slow down. ◍ rule-based query optimization algorithm. Ans: A query optimization technique that uses preset rules and points to determine the best approach to executing a query. ◍ SQL cache. Ans: A shared, reserved memory area that stores the most recently executed SQL statements or PL/SQL procedures, including triggers and functions. Also called procedure cache.
