SUBSTR

Syntax

substr::=

Text description of substr

Purpose

The substring functions return a portion of string, beginning at character position, substring_length characters long. SUBSTR calculates lengths using characters as defined by the input character set. SUBSTRB uses bytes instead of characters. SUBSTRC uses unicode complete characters. SUBSTR2 uses UCS2 codepoints. SUBSTR4 uses UCS4 codepoints.

• If position is 0, it is treated as 1.

• If position is positive, Oracle counts from the beginning of string to find the first character.

• If position is negative, Oracle counts backwards from the end of string.

• If substring_length is omitted, Oracle returns all characters to the end of string. If substring_length is less than 1, a null is returned.

string can be any of the datatypes CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The return value is the same datatype as string. Floating-point numbers passed as arguments to SUBSTR are automatically converted to integers.

Examples

The following example returns several specified substrings of "ABCDEFG":

SELECT SUBSTR('ABCDEFG',3,4) "Substring"
     FROM DUAL;
 
Substring
---------
CDEF

SELECT SUBSTR('ABCDEFG',-5,4) "Substring"
     FROM DUAL;

Substring
---------
CDEF

Assume a double-byte database character set:

SELECT SUBSTRB('ABCDEFG',5,4.2) "Substring with bytes"
     FROM DUAL;

Substring with bytes
--------------------
CD