TSTC ITSE 1345 - Oracle SQL Final Exam Review

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TSTC Waco ITSE 1345 - Oracle SQL Final Exam Review Summer 2011

Explain how LINESIZE, PAGESIZE, and FEEDBACK affect the output of your script

LINESIZE - command determines the total number of characters SQL *Plus displays in on line before beginning a new line.
PAGESIZE - default is 14; when you use the default, you repeat the heading every 14 rows.
FEEDBACK - command returns the number of records returned by a query.

Explain how Substitution Variables are used when writing scripts.

When you want to run the same script repeatedly, but want to be able to change a variable you would use a substitution variable. During the execution of the script the user will be prompted to input the variable to use.

Explain how the SPOOL command is used and what program it can be used in.

The SPOOL command, together with a file name, spools any subsequently issued SQL Plus or SQL command to a file. Just as with other file names, you can add a path to store the file in a directory other than your SQL Plus default directory. SQL Developer does not allow for spooling.

Explain the steps needed to run a script in SQL Developer

Load the file into the SQL Statement Box, by opening the location the file is stored and inserting it into the statement Box. Next you can press the F5 key.

Explain what a static data dictionary view is and how it is used

The static data dictionary stores details about database objects, such as tables, indexes, and views. Whenever a new object is added or an object is changed, data about the object is recorded in the data dictionary.

Explain what is found in the All Objects report folder in SQL Developer

Lists all objects accessible for the chosen database connection. Also lists a helpful dependencies report for accessing change impact.

List the different types of data dictionary views.

USER_, ALL_, DBA_, and V$

Write a statement for SQL*Plus that shows the dictionary.

DESC dict;

SELECT LIST of a subquery in an INSERT statement

SET clause of an UPDATE statement

Is The following statement is correct:
SELECT *
FROM instructor
ORDER BY phone

TRUE

What does the following function return? SELECT LENGTH(NULL),
FROM dual

Null

_________ and __________ functions are opposites of each other and provide a value in a group of rows.

Both MIN and MAX

_________ rows are not allowed in the relational model.

Orphan

___________ subqueries allow you to reference columns from the outer query and execute the inner query repeatedly

Correlated

____________ are useful for analyzing and exploring the relationships within your data

Self-joins

_________________ relationships are always optional relationships.

Recursive

__________________ inserts the current date and time.

SYSDATE

A _____ is a query definition stored in the database that looks just like a table, but does not have any physical rows

x

A _________ subquery returns a single column with a single row

Scalar

A calculation with a null always yields another null.

TRUE

A constraint must have a name in order for it to be disabled.

FALSE

A DML command automatically issues a COMMIT.

FALSE

A function that operates on a single value can have only one input parameter.

FALSE

A join across three tables can be expressed with the ________ join syntax.

ANSI

A space or value of zero is the same as NULL in a schema diagram

FALSE

A transaction is a logical unit of work.

TRUE

All SQL statements contained within a script must end with a semicolon or forward slash, even if they are done in SQL Developer.

TRUE

An outer join includes the result rows returned by an __________ plus extra rows where no matches are found.

Equijoin

Another name for a data dictionary view is __________________ or _________________.

static or dynamic

Checks whether any value in the list makes the condition true.

Any

Checks whether any value in the list makes the condition true.

Any

Comparison operators can compare multiple _________________.

Columns

Converting a text literal to DATE format requires the use of the TO_CHAR function.

TRUE

Dynamic views begin with a ___________.

V$

Explain Flashback queries and how they are used. Give an example of a FLASHBACK_TRANSACTION query and explain what it does row by row.

Orable's flashback query feature allows you to look at values of a query at a specific time in the past, such as before specfic DML statements occured. This can be usefull in case a suer accidentally performs an unintended but committed DML change. It can also be useful if you want to compare previous data to current data.

Explain how Dynamic SQL is used and give an example of a Dynamic SQL statement.

Dynamic SQL is used to be continuously updated by the background processes in the Oracle instance but never by the user.

Explain how Oracle treats locks when a database is being updated and needs to be viewed by other users.

When you issue a INSERT, UPDATE, DELETE, or MERGE statement, Oracle automatically locks the modified rows. The lock prevents other sessions from making changes to these rows. The lock is released when the session initiating change commits or rollsback.

Explain how you can optimize your queries with subqueries and the main advantage of doing so.

Subqueries allow you to nest multiple queries into each other. This gives you the ability to use one statement to break down a problem into individual components. Without nesting queries, you would be required to have multiple queries which could be time consuming and difficult to accomplish. With the ability to nest queries you can breakdown results to get the results you were needing in one statement.

Explain in detail the impact of INDEXES and how they are used by Oracle.

To achieve good performance for data retrieval and data manipulation statements Oracle uses indexes. In the same way you would use an index in the back of a book to quickly find information, Oracle uses indexes to speed up data retrieval. If the appropriate index does not exist on a table, Oracle needs to examine every row (called a full table scan), which can be time consuming.

Explain the differences in how an ANSI Full Outer Join and a Full Outer Join using the UNION Operator work

x

Explain why constraints are used when building tables.

Constraints are used to enforce the business rules of a system. For instance, "The salary of an employee may not be a negative number" may be enforced with a check constraint on the salary column. Constraints also ensure integrity and data consistency among all applications, no matter which program and ease the burden of programming the business rules in individual applications because the database enforces the constraint.

Explicit data type conversion is preferable to Oracle's implicit conversion.

TRUE

How many characters can be stored in the CHAR column/field?

2000

How many characters can you have using the VARCHAR data type?

4000

If a graphical representation of a table's box has __________ it means that the relationship is identifying.

rounded edges

If you are running a version of Oracle that is prior to 9i, it is best to use the ANSI Outer join.

FLASE

In a view you can give a column a different name than it has in the parent table.

TRUE

In SQL Developer field names and table names are shown in the color _______.

Black

Information that is returned after you run your statement are found in the __________ tab in SQL Developer.

Results

Instead of using the Oracle Outer Join Operator or the ANSI syntax, you can achieve the same result with two SQL statements: ____________ and a ____________

Equijoin and correlated subquery

It is always good practice to include the old values in the WHERE clause of UPDATE to ensure that another session or user has not changed the name in the meantime.

TRUE

It is common practice to place a HAVING clause before the GROUP BY clause.

FALSE

It is considered good form to put all SQL commands in all caps.

TRUE

It is not possible to limit or disable constraints using Dynamic SQL scripting.

FALSE

Joins involving multiple columns must always follow the primary key/foreign key relationship path.

TRUE

List 4 aggregate functions

COUNT(registration_date), AVG (capacity), MIN (capacity), MAX (capacity)

List 6 Table-Related Menu Choices

RENAME, COPY, DROP, TRUNCATE, LOCK, & COMMENT

List the reasons that a subquery could not be unnested.

x

List the steps performed by a correlated subquery.

**** Select a row from the outer query, Determine the value of the correlated column, Execute the inner query for each record of the outer query., Feed the results of the inner query to the outer query and evaluate it. It if satisfies the criteria, return the row for output.Select the next record of the outer query and repeat steps 2 through 4 until all the records of the outer query are evaluated.

Match each of the SQL commands on the left with a verb from the list.

Control - Revoke
Define - TRUNCATE
Manipulate - MERGE

NUMBER functions can be nested

TRUE

Oracle prefers that you use the unique index syntax for future compatibility.

FALSE

Oracle uses the outer join operator to indicate that nulls are shown for non-matching rows.

TRUE

Primary key values should always be subject to frequent change.

FALSE

Queries that are found in parentheses are done first, just as in the order of operations when doing mathematical equations.

TRUE

Returns rows if the condition is true for all the values in the list

All

Self-joins are useful for performing comparisons and checking for inconsistencies in data.

TRUE

SQL Developer provides an extensive list of useful reports and offers the capability to create your own user-defined reports

TRUE

SQL Developer's ____________________ option allows you to selectively export certain rows and columns.

Export Data

SQL*Plus is used more than SQL Developer when you need to run scripts.

TRUE

Subqueries can return multiple rows.

TRUE

Substitution variables are limited to the WHERE clause of a statement.

FALSE

The ______ operator compares a list of values for equivalency

ANY

The _______ function adds values together for a group of rows.

SUM

The _______ operator determines common rows.

INTERSECT

The ________ operator cannot compare against a list of values.

LIKE

The __________ operator is inclusive of the two values specified.

BETWEEN

The ___________ operator tests whether a matching row cannot be found.

x

The ____________ clause on a CREATE TABLE statement can specify how much space to allocate.

STORAGE

The ____________ command makes changes permanent.

COMMIT

The ____________ icon allows you to execute multiple statements and emulates SQL *Plus as much as possible.

RUN SCRIPT

The ____________ keywords and the USING clause of the ANSI join syntax are mutually exclusive.

NATURAL JOIN

The _____________ clause determines how rows are grouped.

GROUP BY

The ________________ is a type of statement whereby you retrieve data that exists in one table, but not in another.

MINUS

The ALL operator returns true if any value in the list satisfies the condition.

FALSE

The ALTER SESSION statement can change the session's time zone.

TRUE

The bitmap index is the most common index structure in Oracle.

FALSE

The common column used in the join condition must be listed in the SELECT list.

FALSE

The COUNT function is useful for determining whether a table has data.

TRUE

The COUNT function uses the __________ wildcard.

Asterisk

The crow's foot depicts the M of a 1:M relationship.

TRUE

The data dictionary is used by Oracle externally to build diagrams.

FALSE

The Data tab in SQL Developer allows you to perform all the major DML commands, using the SQL *Plus interface.

FALSE

The data type definitions NUMBER(10) and NUMBER(10,0) are the same.

TRUE

The DECODE function lets you perform if-then-else functionality with the SQL language.

TRUE

The DUAL table can be used for testing functions.

TRUE

The eraser icon removes all statements in SQL *Plus

FALSE

The EXISTS operator can return True, False or Unknown

FALSE

The focus of the logical data model is _____________

business problems

The INSERT statement creates new data in a table only through single rows.

FALSE

The key that most database designers prefer and is chosen by the system is the _____________ key.

Surrogate

The lack of a unique index key is frequently the reason for slow performance of updates and deletions

FALSE

The MIN and MAX functions cannot take other data types as parameters.

FALSE

The MINUS operator shows likenesses between sets of rows.

FALSE

The NEXTVAL and CURRVAL pseudocolumns can be used in which of the following SQL constructs? Select all that apply.

VALUES clause of an INSERT statement

The Nonequijoin can use the ________________ operator to construct joins that are not based on equality of values.

BETWEEN

The number of rows in a table matches the number of columns

FALSE

The ORDER BY clause is allowed in subqueries.

FALSE

The purpose of the HAVING clause is to eliminate___________.

Groups

The query retrieves more than 5 to 15 percent of the rows

The indexed column is part of an expression. In this case, consider creating a function-based index instead

The ROUND function can take only the NUMBER data type as a parameter

FALSE

The ROWID pseudocolumn is not an actual column, but it acts like one.

TRUE

The RTRIM function is useful for eliminating extra spaces in a string.

TRUE

The same function can be used twice in a SELECT statement.

TRUE

The SELECT command always places locks on retrieved rows.

FALSE

The self join is different from other joins because it does not utilize a primary key or a foreign key.

FALSE

The surrogate key generated by a sequence is often used by the DBA and is changed often.

FALSE

The term ____________ ___________ is used to express a join that satisfies the join condition.

INNER JOIN

The time zone displacement value indicates the time difference from _______.

UTC

The TIMESTAMP WITH LOCAL TIME ZONE data type allows fractional seconds.

TRUE

The TRUNC function on a date without a format model truncates the timestamp to 12:00:00 A.M.

TRUE

The using clause of the ANSI join syntax always assumes an equijoin and identical column names.

TRUE

To equijoin a table with another table involves matching the common column value.

TRUE

To join four tables, you must have at least three join conditions.

TRUE

To place a line comment in your SQL statements, you first place a // at the beginning of the line.

FALSE

To restart a sequence at a lower number, you can drop and re-create the sequence.

TRUE

To revert back to a state that happened before you ran your change statement, you issue a ____________ command.

ROLLBACK

UNION ALL does not sort, therefore it is less time consuming to use than the UNION operator.

TRUE

Users can only see changes made to a database once they have been committed.

TRUE

Usually a script only needs to be run and tested one time to make sure that it is functional.

FALSE

What are the main components of a ROWID?

The main components of a ROWID are the data object number, the number of the data block, the numbers of rows within the data block, and the data file number.

What do views do that makes them so useful for security?

hide data

What does SQL stand for?

Structured Query Language

What is Oracle's most popular index storage structure?

B-Tree Index

What is the command you would type into SQL*Plus if you needed to know the definition for each column of a table?

DICT_COLUMNS

What is the data type you can use if you need an unlimited number of textual characters?

CLOB

What is the first column of a composite index called?

leading-edge

What is the keyboard shortcut for the ROLLBACK command?

F12

What is the main difference between the NOT EXISTS and the NOT IN operators?

The way NULL values are treated

What is the maximum value for a column defined as NUMBER(4,2)?

99.99

What is the most common DATE format found in SQL?

DD-MON-YY

What is the name of the key automatically generated from a sequence?

surrogate key

What is the name of the view where you can find the collection of static and data dictionary tables and views, along with their descriptions?

DICTIONARY

What is the Oracle data dictionary called that contains a set of tables and views containing the data about the database?

ALL_OBJECTS

What is the syntax used to indicate that you are using the Oracle Outer Join operator?

+

What is the tab in SQL Developer where data dictionary view information can be found?

Details

When column names on the tables are different, you use the ______ condition.

ON

When disabling a unique or primary key, you can keep the index if you specify the __________________ clause in the ALTER TABLE statement.

KEEP INDEX

When is it not a good idea to use an index?

When the table is small (unless your business rules require you too)

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