====== Search Substring (Expression Function) ======

===== Purpose =====
The **Search Substring** function (SEARCH_SUBSTRING) is used to find the index of a search string found within another string.  The search is case sensitive.

{{::search_substring_initial.png?direct&600|}} 
===== Parameters =====
The **Search Substring** function has four parameters, two of which are required:

==== Find ====

Allowed Inputs: [[Field|field]] value or text string

The first required parameter of the **Search Substring** function is the string that we are looking for. Either use the use the [[Query Builder]] to choose a field that contains the search value or use type a value to search for a text string.
==== Within ====

Allowed Inputs: [[Field|field]] value or text string

The second required parameter is the string that is being search.  It can either be obtained from a field using the Query Builder or from a literal string.
==== Occurrence ====

Allowed Inputs: [[Field|field]] value or a positive number

The third parameter, which is optional, is a number denoting which occurrence of the search value to return the index for. If this option is not used then the first occurrence is used.

==== Start Point ====

Allowed Inputs: omitted or "end"

The fourth parameter, which is optional, is a string used to determine from which end of the string the search starts.  If this parameter is omitted then the search will proceed left to right.  If the parameter is set to "end" then the search will be performed right to left.  If this parameter is used then the third parameter will need to be entered.

===== Output =====

The output of the **Search Substring** function is a number representing the index of the left hand side of the searched string relative to the left hand side of the string being search starting at zero.

===== Example =====

Searches are case sensitive for example SEARCH_SUBSTRING("T","This is a String') will return 0 while SEARCH_SUBSTRING("t","This is a String') will return 11.  The index returned is always relative to the left hand side of the string for example SEARCH_SUBSTRING("i","This is a String',1,'end') returns 13 and SEARCH_SUBSTRING("i","This is a String',1) returns 2.