F_

F_SUBSTR (F_SUBSTR4, F_SUBSTR8) F_BIGSUBSTR

 
substitutable with POSITION
 also use U_SUBSTR

compatibility to FreeUDFLibC
Compatible with UTF-8
Input VARCHAR(8190) String 1 (in which the position of parameter 2 is to be determined), VARCHAR(1024) String 2 (to be determined)
Output INTEGER first position in string 1 where string 2 starts

F_STRSUB

F_STRPOS also use U_SUBSTR

input/output-compatibility to rFunc (STRPOS)
Input VARCHAR(1024) String 1 (to be determined) VARCHAR(8190) String 2 (in which the position of parameter 2 is to be determined),
Output INTEGER first position in string 1 where string 2 starts

 F_SUBSTR, F_STRSUB etc.: Counting starts with 0, if not found -1. 
 F_STRPOS: Counting starts with 1, if not found 0.

Example

 SELECT 13 AS ISCORRECT, F_SUBSTR('John like to drive fast', 'drive') FROM RDB$DATABASE;

Expected results:

   ISCORRECT     F_SUBSTR
 ============ ============
          13           13

Example

 SELECT -1 AS ISCORRECT, F_SUBSTR('John like to drive fast', 'dive') FROM RDB$DATABASE;

Expected results:

   ISCORRECT     F_SUBSTR
 ============ ============
          -1           -1

Example

 SELECT NULL AS ISCORRECT, F_SUBSTR(NULL, NULL) FROM RDB$DATABASE;

Expected results:

   ISCORRECT     F_SUBSTR
 ============ ============
   <null>          <null>

Example

 SELECT 14 AS ISCORRECT, F_STRPOS('drive', 'John like to drive fast') FROM RDB$DATABASE;

Expected results:

   ISCORRECT     F_SUBSTR
 ============ ============
          14           14

Example

 SELECT 0 AS ISCORRECT, F_STRPOS('dive', 'John like to drive fast') FROM RDB$DATABASE;

Expected results:

   ISCORRECT     F_SUBSTR
 ============ ============
          0           0

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