SQL*Plus offers only one format element when it comes to character strings. That element is “A”. “A” is always followed by a number specifying the column width in characters. Character strings shorter than the column width are displayed left-justified within the column. Character strings that exceed the column width are either wrapped or truncated based on the option specified in the COLUMN command. The following example shows a text column that has been 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 that 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. This is shown in the following example:

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

SQL>

While the character format used with ACCEPT specifies a maximum length, it does not specify a minimum length. You can always enter fewer characters than the format calls for, even to the point of entering nothing at all.