Tài liệu Oracle SQL Jumpstart with Examples- P5 docx

170 8.4 Using iSQL*Plus
cuted within the browser HTML page, both of which are stored on the
server running the HTTP server process.
Figure 8.27
Your Customized
Report Running
Web Page.
Figure 8.28
The CDREPORT
Script Was Run
and Displayed.
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8.4 Using iSQL*Plus 171
Chapter 8
This example placed the username, password, and Oracle database net-
work name (SID) in the source code. This is not necessarily a good idea in a
commercial environment from a security perspective. Anyone can view the
source code of an HTML document and retrieve information. It would be
better to modify the HTML in your document so that the user is required
to enter a username and password. Additionally, secure socket layers (SSL)
can be used to encrypt data traveling between a Web browser and the server.
8.4.2 iSQL*Plus versus SQL*Plus
The main features of iSQL*Plus are similar to the features of SQL*Plus or
SQL*Plus Worksheet:

Enter SQL commands in a box and click the Execute button to dis-
play the results. Results can be displayed below the box or in a new
browser window.

Adjust environment settings by clicking the Preferences button, using

a series of radio buttons and boxes to modify settings such as HEAD-
ING, RECSEP, and so on.

Use variables just like SQL*Plus, except you cannot use the ACCEPT
or PROMPT commands to prompt for values. iSQL*Plus displays its
own prompt.
Note: iSQL*Plus allows prompts for input values.

Review and retrieve previous SQL commands by clicking the History
button, much like SQL*Plus Worksheet.
8.4.3 Troubleshooting iSQL*Plus
If there are problems running iSQL*Plus, configuration settings and other
things can be checked on the server.

Check that the port number is the default 7778 value in the file
HTTPD.CONF in the $ORACLE_HOME/Apache/Apache/conf
directory.
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172 8.4 Using iSQL*Plus

The port number should also be in the SETUPINFO.TXT file in the
directory $ORACLE_HOME/Apache/Apache. This file should con-
tain entries such as the following:
http://<hostname>:7778
http://<hostname>:4443
Note: Replace hostname as appropriate.

The file called ORACLE_APACHE.CONF in the
$ORACLE_HOME/Apache/Apache/conf directory must include

the file ISQLPLUS.CONF in the ORACLE_HOME/sqlplus/admin
directory. The include command should be of the following form. Be
sure there are no comments (#) in unexpected places.
include "$ORACLE_HOME/sqlplus/admin/isqlplus.conf"

Try stopping and restarting the HTTP Server, especially if you have
made any changes to any configuration files. A bug in Oracle 9.2 for
Windows 2000 caused errors when starting and stopping the HTTP
Server using both the Windows service and the Apache command on
the Start menu. A solution to this issue is to set the service to Manual
and always start and stop Apache and the HTTP Server with the fol-
lowing commands executed in a DOS shell (the command line):
C:\oracle\ora92\Apache\Apache\apache -k start
C:\oracle\ora92\Apache\Apache\apache - k shutdown
8.4.4 Customizing iSQL*Plus Display
Numerous preferences can be changed from the iSQL*Plus interface on the
client machine. Additionally, on the server there is an HTML cascading
style sheet.
1
This style sheet can be altered to change output appearance.
The HTML cascading style sheet is called IPLUS.CSS and is located in the
$ORACLE_HOME/sqlplus/admin/iplus directory on the server. Changing
the style sheet allows customization of colors and fonts used by iSQL*Plus
when it formats output for queries. Using the same simple query used pre-
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8.4 Using iSQL*Plus 173
Chapter 8
viously in Figure 8.26, Figure 8.29 has an altered appearance as a result of
changes to the style sheet file on the server.

In Figure 8.29, all text color is removed, all background colors apart
from that in the headings is removed, and all borders are removed from
everything but headings. The style sheet has numerous elements. I changed
the following two elements:

The TH or HTML table heading tag or element is changed where
highlighted.
TH {
font : bold 10pt Arial, Helvetica, sans-serif;
color : black;
background : #f0f0f0;
padding : 0px 0px 0px 0px;
}

The combination TABLE, TR, TD element is also changed where
highlighted.
TABLE, TR, TD {
font : 10pt Arial, Helvetica, sans-serif;
Figure 8.29
Changing the
iSQL*Plus Style
Sheet on the Server.
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174 8.5 Endnotes
color : Black;
background : white;
border : 1
padding : 0px 0px 0px 0px;
margin : 0px 0px 0px 0px;

}
This is a quick introduction to iSQL*Plus that should help you get
started with your own experimentation. Remember to review the help
screens provided inside iSQL*Plus for more examples of code and quick
reference to SQL syntax.
This chapter has covered more detail on SQL*Plus and related tools, in
addition to the introductory information provided in Chapter 1. The next
chapter moves back into Oracle SQL and looks at functions, namely single-
row functions.
8.5 Endnotes
1. www.oracledbaexpert.com/menu/DHTML.html
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175

9

Single-Row Functions

In this chapter:



What types of built-in functions are available?



What are single-row functions?



What are the categories of single-row functions?



How do functions work with queries?



What are the options when formatting strings, numbers, and dates?



What are data conversion functions?



How are functions combined?
This chapter uses the queries you have worked with in previous chapters
and expands the way you can use columns by introducing functions. You
will examine the types of functions used for different data types. Finally,
you will experiment with combining functions together for more flexibility.
A function is a built-in PL/SQL program that always returns a single
value. You can use the predefined functions (such as the ones discussed in
this chapter) or you can create your own (see Chapter 24). A function
always returns a single value, as opposed to a procedure, which is a similar
type of program but is able to return more than one value. You can call a
function within a query or other SQL command. You have already seen a
few functions in previous chapters (e.g., NVL and SYSDATE). Before we

examine single-row functions in detail, let’s look at Oracle-provided built-
in functions in general. Grouping functions are covered in Chapter 11, reg-
ular expression functions in Chapter 14, object reference functions in
Chapter 16, and XML functions in Chapter 17.

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176

9.2

Single-Row Functions

9.1 Types of Functions

Oracle divides all functions into the following categories:



Single-Row Functions

. Functions that operate on a single row at a
time. This chapter examines this type of function. For example, the
UPPER() function converts characters to uppercase.



Grouping Functions

. Chapter 11 covers grouping functions in
detail.



Aggregate Functions

. Functions that operate on a group of rows
at one time and return a single row. For example, the COUNT()
function counts the number of rows in a table.



Analytical Functions

. Functions that operate on groups of rows
and return one or more summary rows. For example, the STD-
DEV() OVER() function returns the standard deviation rows
based on values in one or more columns.



Object Reference Functions

.



Functions that manipulate the value in
columns with the REF datatype in object tables. For example, the

DEREF() function returns the value of an attribute in the referenced
object table (see Chapter 16).



User-Defined Functions

. Functions that are built by you and per-
form whatever data manipulations you program them to do. Exam-
ples of user-defined functions are given throughout this book, with
syntactical details in Chapter 24.
This chapter covers many of the dozens of single-row functions available
for your use in queries.

9.2 Single-Row Functions

Single-row functions add a great deal of power to queries. Use functions in
the SELECT clause to modify the appearance of dates, for example. Add
functions to the WHERE clause to help determine which rows to include in
query results. Place functions in the ORDER BY clause to fine-tune sorting.

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9.2

Single-Row Functions 177
Chapter 9

Note:

Placing functions in WHERE and ORDER BY clauses can be detri-

mental to performance.

1

There are so many single-row functions that there is not room to cover
them all in this chapter. However, you will gain experience with the com-
monly used functions. Other more obscure functions are detailed in Oracle
documentation. Single-row functions can be subdivided into the following
categories:



Character or String Functions

. Functions that require a character
value or string as input (see Figure 9.1).



Number Functions

. Functions that require a number as input.
Most of these return a number. For example, the SIGN function
returns -1 if the number is negative, 0 if it is zero, and 1 if it is posi-
tive (see Figure 9.2).



Binary Floating-Point Number Functions

. These func-
tions are new to Oracle Database 10

g

and could possibly be
viewed as a subset of number functions, except that they operate
specifically on binary floating-point numbers (see Figure 9.2).



Datetime Functions

. Functions that require a date value as input
(see Figure 9.3).



Conversion Functions

. Functions that convert one datatype to
another. For example, the TO_CHAR function can convert a date or
number to a character value (see Figure 9.4).



Miscellaneous Functions

. Functions that perform unusual tasks. For
example, the DECODE function acts like an IF-THEN-ELSE con-
struct or CASE statement (see Figure 9.5).
Figures 9.1 through 9.5 show all the different types of single-row func-
tions. Functions highlighted and marked with an asterisk (

*INITCAP

) in
each figure are discussed in this chapter. Additionally, many functions are
referred to in other chapters.


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178

9.2

Single-Row Functions

Figure 9.1

Single-Row String
Functions.

Figure 9.2

Single-Row
Number Functions.

Figure 9.3

Single-Row
Datetime
Functions.

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9.2

Single-Row Functions 179
Chapter 9

Figure 9.4

Single-Row
Conversion
Functions.

Figure 9.5

Single-Row
Miscellaneous
Functions.

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180

9.2

Single-Row Functions

The next sections define all of the functions highlighted in Figures 9.1
and 9.2, divided by their categories. Functions detailed in this chapter are
generally the more useful functions. As already stated, the remaining func-
tions tend to be obscure and seldom used. In fact, some functions included
in this chapter are obscure. Let’s begin with string functions.

9.2.1 String Functions

The string functions manipulate alphanumeric data. In this section, after
each function is defined, an example shows how the function is used and
what it returns.



CONCAT(expression, expression)

. Concatenation of strings is the
adding together of two strings. This function performs the same task
as the string concatenation operator || (see Chapter 7).

CONCAT('Oracle',' Database 10g') = 'Oracle Database 10g'
'Oracle'||' Database '||'10g' = 'Oracle Database 10g'

'My name is '||FIRST_NAME = 'My name is Jim'



LOWER(expression)

,

UPPER(expression

), and

INITCAP(expres-
sion)

. LOWER converts to lowercase, UPPER to uppercase, and
INITCAP to mixed case (first letter of each word in uppercase).

INITCAP('oracle certified professional')
= 'Oracle Certified Professional'



INSTR(expression, substring [, position [, occurrence]])

. Returns
the position of a substring within a string (the first character in the
string is at position 1). The position and occurrence parameters are
optional. The position parameter determines a start point to search
from, and occurrence indicates which duplicate, if any, of the sub-

string should be matched. In the following example, the second
occurrence of the string 10g begins at position 19:

INSTR('oracle 10g oracle 10g oracle 10g','10g',1,2) = 19



LENGTH(expression)

. The length in characters of a string.

LENGTH('oracle certified professional') = 29
LENGTH(LAST_NAME) = length of the data in the column



LPAD(expression, n [, expression])

and

RPAD(expression, n [,
expression])

. Left or right pad a string from the left or the right (start
or end of the string) with the specified characters in the second string,
up to a string length of

n

characters.

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9.2

Single-Row Functions 181
Chapter 9

LPAD('oracle',10,'X') = 'XXXXoracle'
RPAD('oracle',10,'X') = 'oracleXXXX'

Note:

Padding a string is sometimes referred to as filling a string.



TRIM([[LEADING|TRAILING|BOTH] character FROM]
expression), LTRIM(expression, string-set),

and

RTRIM(expres-
sion, string-set)

. LTRIM and RTRIM will remove from the left and
the right of the string, respectively, any characters contained within
the string set, until a character not in the string set is found. The
LTRIM and RTRIM functions are less useful than the TRIM func-

tion. TRIM will remove characters from the string from the left, the
right, or both. In its simplest form, TRIM can be used to remove
leading and trailing spaces from a string.

TRIM(' oracle ') = 'oracle'

Remember that spaces embedded between other characters do not
get removed, until a character not in the string set is found. As a
result, for the next example there is no change.

TRIM(' o r a c l e ') = 'o r a c l e'
TRIM( LEADING '-' FROM '---608-444-3029') = '608-444-3029'



REPLACE(expression, search [, replace])

and

TRANS-
LATE(expression, search [, replace])

. REPLACE will replace every
occurrence of the search string with the replacement string. Where
the REPLACE function matches any search string within the string,
TRANSLATE will match each character between the search and
replace strings by the position of characters in both the search and
replace strings. Phew! In simple terms, REPLACE replaces groups of
characters and TRANSLATE translates individual characters.

REPLACE(' o r a c l e',' ','') = 'oracle'
REPLACE('My dog has fleas.','as','odd')
= 'My dog hodd fleodd.'

In the first TRANSLATE function example following, nothing is
changed because the space in the search string has no corresponding
value in the replace string.

TRANSLATE(' o r a c l e ','oracle ','12345X')
= '12345X'
TRANSLATE('My dog has fleas.','agf','AGF')
= 'My doG hAs FleAs.'

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182

9.2

Single-Row Functions



SUBSTR(expression, [-]position[, length])

. The SUBSTR func-
tion returns a portion of a string. If the length parameter is omitted,
then all characters after the value of position are returned. If the posi-
tion parameter is positive, then the substring value is extracted from

the left of the string; otherwise, if the parameter is negative, the value
is extracted from the right (end) of the string.

SUBSTR('oracle certified professional', 8,9)
= 'certified'
SUBSTR('oracle certified professional',-12,12)
= 'professional'

Here is a quick example using some of the string functions men-
tioned previously. Figure 9.6 shows the results. The query shows the
complete value of the NAME column, followed by the length of the
value, a section of the name, and finally, the position of the second
occurrence of the letter “a” in the name. Notice that the INSTR func-
tion returns zero if it cannot find a match.
SELECT NAME, LENGTH(NAME) "Length"
, SUBSTR(NAME,5,5) "Letters 5 thru 9"
, INSTR(NAME,'a',1,2) "Second a"
FROM ARTIST;
Now let’s proceed to number functions.
9.2.2 Number Functions
Number functions require numbers, not strings, as input. They nearly
always return a numeric value.

ABS(n). Finds an absolute value of a number. An absolute value
function returns the positive or unsigned value of a negative or posi-
tive number.
ABS(-125) = 125
ABS(125) = 125

CEIL(n) and FLOOR(n). Ceiling and floor are similar to rounding

and truncating functions. Ceiling returns the next integer greater
than n. Floor returns the next integer less than n.
CEIL(1.1) = 2
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9.2 Single-Row Functions 183
Chapter 9
FLOOR(1.9) = 1

MOD(m, n). MOD is the modulus or remainder function, which
returns the remainder of the first value divided by the second value (m
divided by n). The first value is returned if the second value is zero.
MOD(5,2) = 1
MOD(4,0) = 4
MOD(9,3) = 0
MOD(23,4) = 3

POWER(m, n). The exponential function raises m to the power of n
(the nth power).
POWER(2,3) = 8 (2
3
= 2 * 2 * 2 = 4 * 2 = 8)

ROUND(n [, places]). ROUND is a proper mathematical rounding
function as opposed to the CEIL and FLOOR functions. For the
ROUND function, a decimal 5 and over will be rounded up and
below 5 will be rounded down. The third example following is
rounded to two decimal places and the fourth to three decimal places.
Figure 9.6
Some String

Functions.
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184 9.2 Single-Row Functions
ROUND(1.4) = 1
ROUND(1.5) = 2
ROUND(1.42356,2) = 1.42
ROUND(1.42356,3) = 1.424
ROUND(18755.24,-2) = 18800

SIGN(n). Returns –1 if negative, 0 if 0, and 1 if positive.
SIGN(-5032) = –1
SIGN(0) = 0
SIGN(5000) = 1

SQRT(n). Calculates the square root of a number.
SQRT(4) = 2 (2 * 2 = 4)

TRUNC(n [, places]). TRUNC is a truncate function. A truncate
function always rounds down by removing trailing numerals from a
number, effectively rounding down regardless of the .5 cutoff value.
TRUNC can also truncate both sides of the decimal point.
TRUNC(147.65,1) = 147.6
TRUNC(147.65,-2) = 100

Other Mathematical Functions. The following functions perform
obscure mathematical or trigonometric calculations. These types of
functions are rarely used other than in financial or numerically
related applications. Some of these functions are listed here. There are
many other Oracle built-in functions to do all sorts of weird and

wonderful things (see Oracle documentation).

SIN(n), COS(n), and TAN(n). Sine, cosine, and tangent.

ASIN(n), ACOS(n), and ACOS(n). Arcsine, arccosine, and arctan-
gent (the inverse of sine, cosine, and tangent).

SINH(n), COSH(n), and TANH(n). Hyperbolic sine, cosine, and
tangent.

EXP(n), LN(n), and LOG(n). e raised to the nth power, the natural
logarithm, and the logarithm.
Here is a query using some of the number functions mentioned.
The query uses the STUDIOTIME table and applies various func-
tions to the AMOUNT_CHARGED column values. The result is
shown in Figure 9.7.
SELECT ST.ARTIST_ID, ST.AMOUNT_CHARGED "Amount"
, ROUND(ST.AMOUNT_CHARGED,1) "Rounded to one decimal"
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9.2 Single-Row Functions 185
Chapter 9
, ROUND(ST.AMOUNT_CHARGED,-1) "Rounded to tens"
, TRUNC(ST.AMOUNT_CHARGED) "Truncated"
FROM STUDIOTIME ST
WHERE ROWNUM < 15;
9.2.2.1 Binary Floating-Point Number Functions
As already mentioned, these functions are new to Oracle Database 10g and
could possibly be viewed as a subset of number functions, except that they
operate specifically on binary floating-point numbers. This section is par-

tially repeated from Chapter 2.

TO_BINARY_DOUBLE(expression, format) and TO_BINARY_
FLOAT(expression, format) allow for conversions. Essentially, these
functions are conversion functions, but they are listed here because
they deal with binary floating-point numbers.

NANVL(value, replace). NANVL returns a replacement value if the
initial value is not a number.
Figure 9.7
Number Functions
Return Results
Based on the
Column Value.
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186 9.2 Single-Row Functions

REMAINDER(n, m). This function is a remainder or modulus
function specifically for binary floating-point numbers.
The next section covers date functions.
9.2.3 Date Functions

ADD_MONTHS(date, months), NEXT_DAY(date, weekday),
LAST_DAY(date), and MONTHS_BETWEEN(date, date).
ADD_MONTHS will add or subtract a number of months to a date
where differences in the number of days in months default to the last
day in the resulting month. NEXT_DAY finds the first day from the
date specified for the day of the week in the string contained in the
second parameter. LAST_DAY finds the last day in the month.

MONTHS_BETWEEN will return the number of months between
two dates.
ADD_MONTHS('27-AUG-02',4) = 27-DEC-02
NEXT_DAY('27-AUG-02','MONDAY') = 02-SEP-02
LAST_DAY('27-AUG-02') = 31-AUG-02
MONTHS_BETWEEN('27-AUG-02','01-JAN-02')
= 7.83870968 months
Note: In the examples listed, note how dates are listed as strings and a
TO_DATE conversion function is not required. This is because DD-
MON-YY is the default date format and there is an implicit string-to-date
datatype conversion. The default date format can be altered. Datatypes are
covered in Chapter 16.

SYSDATE, CURRENT_DATE, CURRENT_TIMESTAMP(preci-
sion), LOCALTIMESTAMP(precision), and SYSTIMESTAMP.
SYSDATE and CURRENT_DATE find the system date setting on
the database server where CURRENT_DATE is timezone sensitive.
The other functions all provide different variations on timestamps.
SQL> SELECT SYSDATE FROM DUAL;
SYSDATE
--------------
23-JAN-04
SQL> SELECT SYSTIMESTAMP FROM DUAL;
SYSTIMESTAMP
------------------------
23-JAN-04 01.03.20.661000 AM -05:00
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9.2 Single-Row Functions 187
Chapter 9


ROUND(date [, format]) and TRUNC(date [, format]). These two
functions round up or truncate dates according to the format specifi-
cation. See Table 9.1 with date formatting rules for the ROUND and
TRUNC functions.
Some examples of date ROUND and TRUNC functions are as
follows. Let’s say that our current date is 26-AUG-02.
ROUND(SYSDATE,'YEAR') = 01-JAN-03
TRUNC(SYSDATE,'YEAR') = 01-JAN-02
ROUND(SYSDATE,'MONTH') = 01-SEP-02
TRUNC(SYSDATE,'MONTH') = 01-AUG-02
ROUND(SYSDATE,'WW') = 27-AUG-02
TRUNC(SYSDATE,'WW') = 20-AUG-02

EXTRACT (format, date). The EXTRACT date function is proba-
bly one of the most useful and largely unknown date functions. For-
mat settings are simple, specific, and can be YEAR, MONTH, DAY,
HOUR, MINUTE, SECOND, or various TIMEZONE options.
Table 9.1 Some of the ROUND and TRUNC Function Date Formatting
Format Characters Rounding and Truncating
CC
The first year in a century.
YYYY, YEAR, YY
The nearest year, rounds up on July 1st.
Q
The nearest quarter, rounds up on the 16th of month two.
MONTH, MON, MM
The nearest month, rounds up on the 16th.
WW
The same day of the week as the first day of the year.

W
The same day of the week as the first day of the month.
DDD, DD
The day.
DAY, D
The first day of the week.
HH, HH12, HH24
The hour (HH24 is a 24-hour clock).
MI
The minute.
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188 9.2 Single-Row Functions
Two examples in the following two queries have their results shown
in Figure 9.8.
SELECT EXTRACT(YEAR FROM DATE '2004-02-09') AS YEAR
, EXTRACT(MONTH FROM DATE '2004-02-09') AS MONTH
, EXTRACT(DAY FROM DATE '2004-02-09') AS DAY
FROM DUAL;
SELECT EXTRACT(YEAR FROM SYSDATE) AS YEAR
, EXTRACT(MONTH FROM SYSDATE) AS MONTH
, EXTRACT(DAY FROM SYSDATE) AS DAY
FROM DUAL;
Looking at some general date function examples, the next query uses
several date functions. The final expression uses the SYSDATE function
and subtracts two dates. The results are in days, so to help compare the
MONTHS_BETWEEN function and the next column, that following col-
Figure 9.8
The EXTRACT
Function Retrieves

Parts of Dates.
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9.2 Single-Row Functions 189
Chapter 9
umn is divided by the average number of days per month (30.44). The two
values Months-1 and Months-2 are very close but not identical. This is a
rather odd example, but Figure 9.9 shows the result.
SELECT SESSION_DATE
, ADD_MONTHS(SESSION_DATE,3) "Plus 3 Months"
, ROUND(SESSION_DATE,'Month') "Round off"
, MONTHS_BETWEEN(SYSDATE,DUE_DATE) "Months-1"
, (SYSDATE-DUE_DATE)/30.44 "Months-2"
FROM STUDIOTIME
WHERE ROWNUM < 15;
The next section examines datatype conversion functions.
Figure 9.9
Date Functions Use
Oracle Database
10g’s Standard
Date Output
Format.
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