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36 Cards in this Set
- Front
- Back
ADD_MONTHS
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Function that adds calendar months to a date.
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ANY operator
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Compares value to each value returned by the subquery.
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Arc
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A curved line. An arc is used to represent an exclusive relationship in an entity-relationship diagram
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Arithmetic expression
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A mathematical equation.
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Artificial attribute
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A created attribute that does not occur in nature (example: a student id).
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Artificial UID
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A unique identifier that does not occur in nature, usually an artificial attribute.
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Attribute
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Characteristic, something that describes, quantifies or specifies an entity.
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Barred relationship
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A relationship that participates in an entity's unique identifier.
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BFILE
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Binary data stored in an external file; up to 4 gigabytes.
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BLOB
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Binary large object data up to 4 gigabytes.
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CACHE/NOCACHE
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Specifies how many values the Server pre-allocates and keeps in memory.
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Cascade barred relationship
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A series of barred relationships between successively connected entities. Cascade barred relationships imply that the unique identifier of each entity in the chain is carried down to the entity on the next level.
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CASCADE constraint
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Constraints referring to dropped columns will also be dropped.
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CHAR(size)
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The CHAR data type stores fixed-length character strings. (Size) refers to the maximum number of characters. The database allocates a fixed space designated by (size), regardless of how many characters the actual data takes up. The default size is 1, the max size is 2000.
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Character functions
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Functions that accept character data as input and can return both character and numeric values.
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CHECK constraint
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Specifies a condition that must be true for each row of data.
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CLOB
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Character large object data up to 4 gigabytes.
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COALESCE
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Returns the first non-null expression in the list.
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Column level constraint
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References a single column and is defined within a specification for the owning column.
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COMMENT ON TABLE
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Command to add comments to a table or column.
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Complex view
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Derives data from more than one table, contains functions or groups of data, and does not always allow DML operations through the view.
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Composite UID
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A unique identifier that is a combination of attributes and/or relationships.
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CONCAT
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Merges the first character value to the second character value; equivalent to concatenation operator (||).
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What is the purpose of pseudo columns? What are two examples of pseudo columns?
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Psuedocolumns are columns that are part of a select statement but dont actually exist as column objects in a database table.
Two examples are ROWNUM - returns a number that indicates the order of the row that Oracle returns. ROWID. - returns the address of the row in the database |
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Define START_WITH and CONNECT_BY
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In Oracle PL/SQL, the START WITH clause appears in hierarchical SQL queries and is used to query data with Master-Detail relationships. It marks a node in the tree which is considered as the starting node or level of the tree structured data. A scalar value or subquery can be used to assign the root of the query.
It is mandatory for use with the CONNECT_BY clause, which indicates relationship between a node and subnode. The parent row can be identified with the PRIOR keyword. Note that START WITH clause is an optional clause in hierarchical queries. Example Syntax: SELECT [COLUMNS] FROM TABLE_NAME START WITH [COLUMN] = [ROOT NODE VALUE] CONNECT BY [CONDITION] Example Usage: The SQL query below lists Employees reporting to their Managers at different levels. SELECT level, LPAD(ename,level*5,' ') ename FROM employee start with empno=100 CONNECT_BY by nocycle prior empno = mgr / |
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What are sequences in Oracle?
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Sequences are database objects from which multiple users can generate unique integers. The sequence generator generates sequential numbers, which can help to generate unique primary keys automatically, and to coordinate keys across multiple rows or tables.
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What are sequences in Oracle?
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Sequences are database objects from which multiple users can generate unique integers. The sequence generator generates sequential numbers, which can help to generate unique primary keys automatically, and to coordinate keys across multiple rows or tables.
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What are the six different normal forms
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• First Normal Form – If all underlying domains contain atomic values only.
• Second Normal Form – If it is in first normal form and every non key attribute is fully functionally dependent on primary key. • Third Normal Form - If it is in 2nd normal form and every non key attribute is non transitively dependent on the primary key. • Boyce Codd Normal Form - A relation R is in BCNF if and only every determinant is a candidate key. • Fourth Normal Form • Fifth Normal Form |
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1NF-First normal form
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Two versions: E.F. Codd (1970) C.J. Date (2003)1970 [1] and 2003 [9]"Table faithfully represents a relation primarily meaning it has at least one candidate key"
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2NF-Second normal form
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E.F. Codd1971 [2]No non-prime attribute in the table is functionally dependent on a proper subset of any candidate key
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3NF-Third normal form
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Two versions: E.F. Codd (1971)C. Zaniolo (1982) 1971 [2] and 1982 [10]"Every non-prime attribute is non-transitively dependent on every candidate key in the table. The attributes that do not contribute to the description of the primary key are removed from the table. In other words
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EKNF-Elementary Key Normal Form
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C. Zaniolo1982 [10]Every non-trivial functional dependency in the table is either the dependency of an elementary key attribute or a dependency on a superkey
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BCNF-Boyce–Codd normal form
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Raymond F. Boyce and E.F. Codd1974 [11] Every non-trivial functional dependency in the table is a dependency on a superkey
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4NF-Fourth normal form
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Ronald Fagin 1977 [12]Every non-trivial multivalued dependency in the table is a dependency on a superkey
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5NF-Fifth normal form
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Ronald Fagin 1979 [13]Every non-trivial join dependency in the table is implied by the superkeys of the table
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DKNF-Domain/key normal form
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Ronald Fagin 1981 [14]Every constraint on the table is a logical consequence of the table's domain constraints and key constraints
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