Sams Teach Yourself SQL in 21 Days, Fourth Edition

Conversion Functions

These three conversion functions provide a handy way of converting one type of data to another. These examples use the table CONVERSIONS.

SQL> SELECT * FROM CONVERSIONS;

NAME              TESTNUM
--------------- ---------
40                     95
13                     23
74                     68

The NAME column is a character string 15 characters wide, and TESTNUM is a number.

TO_CHAR

The primary use of TO_CHAR is to convert a number into a character. Different implementations may also use it to convert other data types, like Date, into a character, or to include different formatting arguments. The next example illustrates the primary use of TO_CHAR:

SQL> SELECT TESTNUM, TO_CHAR(TESTNUM)
  2  FROM CONVERT;

  TESTNUM TO_CHAR(TESTNUM)
--------- -----------------
       95                95
       23                23
       68                68

It is not very ...