Oracle SQLPlus [Electronic resources] : The Definitive Guide, 2nd Edition نسخه متنی

B.2 Formatting Character Strings

SQL*Plus
offers only one
format element when it comes to
character strings: A. A is always followed by a number specifying the
column width in characters. Character strings shorter than the column
width are displayed as left-justified within the column. Character
strings that exceed the column width are wrapped or truncated based
on the option specified in the COLUMN command. The following example
shows a text column formatted wide enough to display the entire
character string:

SQL> COLUMN a FORMAT A40
SQL> SELECT 'An apple a day keeps the doctor away.' A
2 FROM dual;
A
----------------------------------------
An apple a day keeps the doctor away.

You can format the column so it is 18 characters wide, which results
in the text being wrapped
within that
space:

SQL> COLUMN a FORMAT A18
SQL> SELECT 'An apple a day keeps the doctor away.' A
2 FROM dual;
A
------------------
An apple a day kee
ps the doctor away
.

By default, SQL*Plus wraps the text right in the middle of a word if
necessary. You can use the WORD_WRAPPED
option
of the COLUMN command to wrap text only at
word boundaries:

SQL> COLUMN a FORMAT A18 WORD_WRAPPED
SQL> SELECT 'An apple a day keeps the doctor away.' A
2 FROM dual;
A
------------------
An apple a day
keeps the doctor
away.

You also have the ability to truncate text at the column boundary:

SQL> COLUMN a FORMAT A18 TRUNCATE
SQL> SELECT 'An apple a day keeps the doctor away.' A
2 FROM dual;
A
------------------
An apple a day kee When used with the ACCEPT
command, a character format defines the maximum number of characters
SQL*Plus will accept from the user:

SQL> ACCEPT some_text CHAR FORMAT A10 thisthatthen
"thisthatthen" does not match input format "A10"
SQL>

Although the character format used with ACCEPT specifies a maximum
length, it doesn't specify a minimum length. You can
enter fewer characters than the format calls for, even to the point
of entering nothing at all.