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Oracle® Database SQL Language Reference
11g Release 2 (11.2)

Part Number E17118-03
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INSTR

Syntax

Description of instr.gif follows
Description of the illustration instr.gif

Purpose

The INSTR functions search string for substring. The search operation is defined as comparing the substring argument with substrings of string of the same length for equality until a match is found or there are no more substrings left. Each consecutive compared substring of string begins one character to the right (for forward searches) or one character to the left (for backward searches) from the first character of the previous compared substring. If a substring that is equal to substring is found, then the function returns an integer indicating the position of the first character of this substring. If no such substring is found, then the function returns zero.

INSTR accepts and returns positions in characters as defined by the input character set, with the first character of string having position 1. INSTRB uses bytes instead of characters. INSTRC uses Unicode complete characters. INSTR2 uses UCS2 code points. INSTR4 uses UCS4 code points.

Both string and substring can be any of the data types CHAR, VARCHAR2, NCHAR, NVARCHAR2, CLOB, or NCLOB. The value returned is of NUMBER data type.

Both position and occurrence must be of data type NUMBER, or any data type that can be implicitly converted to NUMBER, and must resolve to an integer. The default values of both position and occurrence are 1, meaning Oracle begins searching at the first character of string for the first occurrence of substring. The return value is relative to the beginning of string, regardless of the value of position.

See Also:

Table 3-10, "Implicit Type Conversion Matrix" for more information on implicit conversion

Examples

The following example searches the string CORPORATE FLOOR, beginning with the third character, for the string "OR". It returns the position in CORPORATE FLOOR at which the second occurrence of "OR" begins:

SELECT INSTR('CORPORATE FLOOR','OR', 3, 2) "Instring"
  FROM DUAL;
 
  Instring
----------
        14

In the next example, Oracle counts backward from the last character to the third character from the end, which is the first O in FLOOR. Oracle then searches backward for the second occurrence of OR, and finds that this second occurrence begins with the second character in the search string :

SELECT INSTR('CORPORATE FLOOR','OR', -3, 2) "Reversed Instring"
  FROM DUAL;
 
Reversed Instring
-----------------
                2

The next example assumes a double-byte database character set.

SELECT INSTRB('CORPORATE FLOOR','OR',5,2) "Instring in bytes"
  FROM DUAL;

Instring in bytes
-----------------
               27