|Oracle® Database SQL Language Reference
11g Release 2 (11.2)
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INSTR functions search
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.
position is an nonzero integer indicating the character of
string where Oracle Database begins the search—that is, the position of the first character of the first substring to compare with
position is negative, then Oracle counts backward from the end of
string and then searches backward from the resulting position.
occurrence is an integer indicating which occurrence of
string Oracle should search for. The value of
occurrence must be positive. If
occurrence is greater than 1, then the database does not return on the first match but continues comparing consecutive substrings of
string, as described above, until match number
occurrence has been found.
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.
string can be any of the data types
NCLOB. The exceptions are
INSTR4, which do not allow
string to be a
substring can be any of the data types
The value returned is of
NUMBER data type.
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
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
See Also:Table 3-10, "Implicit Type Conversion Matrix" for more information on implicit conversion
The following example searches the string
FLOOR, beginning with the third character, for the string "
OR". It returns the position in
FLOOR at which the second occurrence of "
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
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