To obtain the structure of an Oracle table, the command to use is:
Answer: B
Correct answer: DESCRIBE [ TableName ].
DESCRIBE, or DESC for short, lists the columns of a table or view with their datatypes and whether they accept nulls. It is a SQL*Plus command rather than SQL, so it takes no semicolon, and it works on views and procedures as well as tables.
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If there is only one statement and no ambiguity about what is wanted, Oracle will treat the semicolon and slash as the same.
Answer: A
Correct answer: True
With a single unambiguous statement in the buffer, ending it with a semicolon and typing a slash on the next line have the same effect: the statement is executed. The two are not interchangeable in general, however - a PL/SQL block contains semicolons within its own body, so only a slash can submit it.
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SQL*Plus will finish the statement and execute it when the user types in this:
Answer: C
Correct answer: A semicolon ( ; ) followed by [Enter].
The semicolon terminates the statement and submits it in one action. The forward slash on a line of its own does something slightly different: it executes whatever is currently in the buffer, which is how a statement is re-run or how a PL/SQL block, whose body contains semicolons of its own, is finally submitted.
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Oracle commands, column names, table names, view names and all other database elements are case sensitive.
Answer: B
Correct answer: False
They are case insensitive. Commands, table names, column names and view names may be written in any case and are matched the same way, which is why SELECT * FROM Customer and select * from CUSTOMER are identical. Case matters only within quoted strings, and in identifiers deliberately created inside double quotes.
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The only time that case matters is inside quotation marks of strings.
Answer: A
Correct answer: True
Case is significant only where the characters are data rather than names: inside a quoted string literal, so that WHERE name = 'Smith' does not match SMITH. Everything else - keywords, table names, column names - is matched without regard to case. Identifiers created inside double quotes are the one further exception.
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The default extension for an Oracle SQL*Plus file is:
Answer: D
Correct answer: .sql.
SQL*Plus assumes an extension of .sql, so a script called load.sql can be run as @load or START load with the extension left off. Files with other extensions must be named in full.
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In creating a procedure, you may get a message if you have compile errors. Which of the following is true?
Answer: C
Correct answer: To see the errors, enter SHOW ERRORS in SQL*Plus.
SQL*Plus reports only that the procedure was created with compilation errors; the errors themselves must be asked for with SHOW ERRORS. The line numbers it then gives are counted from the start of the CREATE statement, which will not match a text editor’s numbering unless the statement begins on line one of the file.
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Oracle will let you define Notepad as your default editor, and whenever you type NOTEPAD, SQL*Plus will invoke Notepad.
Answer: B
Correct answer: False
The first half is right and the second wrong. An editor is defined once, with DEFINE _EDITOR, and is then invoked by typing EDIT - not by typing the editor’s own name, which SQL*Plus would not recognise as a command. The point of the arrangement is that scripts using EDIT work whatever editor has been chosen.
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You can check on the status of tables with the DESCRIBE or DESC command.
Answer: A
Correct answer: True
DESCRIBE, abbreviated DESC, lists the columns of a table or view with their datatypes and their nullability. It is the quickest way of confirming what a table actually contains before writing a statement against it, and it works on views and procedures too.
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Oracle allows the ORDER BY clause in view definitions.
Answer: A
Correct answer: True
This is the exception to the standard. SQL-92 forbids ORDER BY in a view definition, on the ground that a view is a relation and a relation is unordered; Oracle permits it. Note that the ordering is not guaranteed to survive a query against the view that imposes its own ordering or joins to something else.
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