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Chapter 2: Retrieving Information from Database Tables
■Pseudo column:
･ROWID
which is used internally by the Oracle database to store the physical location of the row. A rowid is an 18-digit number that is represented as a base-64 number.
･ROWNUM
■Table dual
dual table has one VARCHAR2 column named dummy and contains a single
row with the value X.
■Using the LIKE Operator
You use the LIKE operator in a WHERE clause to search a string for a pattern. You specify patterns using a combination of normal characters and the following two wildcard characters:
･Underscore (_) Matches one character in a specified position
･Percent (%) Matches any number of characters beginning at the specified position
･'%\%%' ESCAPE '\'
■NOT IN returns false if a value in the list is null
■You can place the outer join operator on either side of the join operator, but you always place it on the opposite side of the column that contains the null value.
Chapter 3: Using SQL*Plus
SQL> help
HELP
----
Accesses this command line help system. Enter HELP INDEX for a list
of topics.
In iSQL*Plus, click the Help button to display iSQL*Plus help.
HELP [topic]
SQL> help index
Enter Help [topic] for help.
@ COPY PAUSE SHUTDOWN
@@ DEFINE PRINT SPOOL
/ DEL PROMPT SQLPLUS
ACCEPT DESCRIBE QUIT START
APPEND DISCONNECT RECOVER STARTUP
ARCHIVE LOG EDIT REMARK STORE
ATTRIBUTE EXECUTE REPFOOTER TIMING
BREAK EXIT REPHEADER TTITLE
BTITLE GET RESERVED WORDS (SQL) UNDEFINE
CHANGE HELP RESERVED WORDS (PL/SQL) VARIABLE
CLEAR HOST RUN WHENEVER OSERROR
COLUMN INPUT SAVE WHENEVER SQLERROR
COMPUTE LIST SET
CONNECT PASSWORD SHOW
Chapter 4: Using Simple Functions
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