POSITION scalar function

The schema is SYSIBM.

The POSITION function returns the starting position of the first occurrence of one string (called the search-string) within another string (called the source-string). If search-string is not found and neither argument is null, the result is zero. If the search-string is found, the result is a number from 1 to the actual length of source-string, expressed in the string unit that is explicitly specified. The search is done using the collation of the database, unless search-string or source-string is defined as FOR BIT DATA, in which case the search is done using a binary comparison.

If source-string has an actual length of 0, the result of the function is 0. If search-string has an actual length of 0 and source-string is not null, the result of the function is 1.

search-string

An expression that specifies the string that is the object of the search. The expression must return a value that is a built-in CHAR, VARCHAR, GRAPHIC, VARGRAPHIC, BLOB, numeric, or datetime data type. If the value is not a CHAR, VARCHAR, GRAPHIC, VARGRAPHIC or BLOB data type, it is implicitly cast to VARCHAR before evaluating the function. The expression cannot be a BLOB file reference variable. The expression can be specified by any of the following:

• A constant
• A special register
• A host variable
• A scalar function whose operands are any of the above
• An expression that concatenates (using CONCAT or ||) any of the above
• An SQL procedure parameter

These rules are similar to those that are described for pattern-expression for the LIKE predicate.

source-string

The expression must return a value that is a built-in string, numeric, or datetime data type. If the value is not a string data type, it is implicitly cast to VARCHAR before evaluating the function. The expression can be specified by any of the following:

• A constant
• A special register
• A host variable (including a locator variable or a file reference variable)
• A scalar function
• A large object locator
• A column name
• An expression that concatenates (using CONCAT or ||) any of the above

CODEUNITS16, CODEUNITS32, or OCTETS

Specifies the string unit of the result. CODEUNITS16 specifies that the result is to be expressed in 16-bit UTF-16 code units. CODEUNITS32 specifies that the result is to be expressed in 32-bit UTF-32 code units. OCTETS specifies that the result is to be expressed in bytes.

If a string unit is specified as CODEUNITS16 or CODEUNITS32, and search-string or source-string is a binary string or bit data, an error is returned (SQLSTATE 428GC). If a string unit is specified as OCTETS and search-string and source-string are binary strings, an error is returned (SQLSTATE 42815).

If a locale-sensitive UCA-based collation is used for this function, then the CODEUNITS16 option offers the best performance characteristics.

For more information about CODEUNITS16, CODEUNITS32, and OCTETS, see "String units in built-in functions" in "Character strings".

The first and second arguments must have compatible string types. For more information on compatibility, see "Rules for string conversions". In a Unicode database, if one string argument is character (not FOR BIT DATA) and the other string argument is graphic, then the search-string is converted to the data type of the source-string for processing. If one argument is character FOR BIT DATA, the other argument must not be graphic (SQLSTATE 42846).

The result of the function is a large integer. If any argument can be null, the result can be null; if any argument is null, the result is the null value.

Examples:

• Select the RECEIVED column, the SUBJECT column, and the starting position of the string 'GOOD BEER' within the NOTE_TEXT column for all rows in the IN_TRAY table that contain that string.

     SELECT RECEIVED, SUBJECT, POSITION('GOOD BEER', NOTE_TEXT, OCTETS)
     FROM IN_TRAY
     WHERE POSITION('GOOD BEER', NOTE_TEXT, OCTETS) <> 0

• Find the position of the character 'ß' in the string 'Jürgen lives on Hegelstraße', and set the host variable LOCATION with the position, as measured in CODEUNITS32 units, within the string.

     SET :LOCATION = POSITION(
       'ß', 'Jürgen lives on Hegelstraße', CODEUNITS32
     )

  The value of host variable LOCATION is set to 26.
• Find the position of the character 'ß' in the string 'Jürgen lives on Hegelstraße', and set the host variable LOCATION with the position, as measured in OCTETS, within the string.

     SET :LOCATION = POSITION(
       'ß', 'Jürgen lives on Hegelstraße', OCTETS
     )

  The value of host variable LOCATION is set to 27.
• The following examples work with the Unicode string '&N~AB', where '&' is the musical symbol G clef character, and '~' is the non-spacing combining tilde character. This string is shown below in different Unicode encoding forms:

  	'&'	'N'	'~'	'A'	'B'
  UTF-8	X'F09D849E'	X'4E'	X'CC83'	X'41'	X'42'
  UTF-16BE	X'D834DD1E'	X'004E'	X'0303'	X'0041'	X'0042'

  Assume that the variable UTF8_VAR contains the UTF-8 representation of the string.

     SELECT POSITION('N', UTF8_VAR, CODEUNITS16),
       POSITION('N', UTF8_VAR, CODEUNITS32),
       POSITION('N', UTF8_VAR, OCTETS)
     FROM SYSIBM.SYSDUMMY1

  returns the values 3, 2, and 5, respectively.
  Assume that the variable UTF16_VAR contains the UTF-16BE representation of the string.

     SELECT POSITION('B', UTF16_VAR, CODEUNITS16),
        POSITION('B', UTF16_VAR, CODEUNITS32),
        POSITION('B', UTF16_VAR, OCTETS)
     FROM SYSIBM.SYSDUMMY1

  returns the values 6, 5, and 11, respectively.
• In a Unicode database created with the case insensitive collation UCA500R1_LEN_S1, find the position of the word 'Brown' in the phrase 'The quick brown fox'.

  SET :LOCATION = POSITION('Brown', 'The quick brown fox', CODEUNITS16)

  The value of the host variable LOCATION is set to 11.