Returns the start index of a the first occurrence of string expression inside another string expression.
Parameters list:
If the string to search is varchar(max), nvarchar(max) or varbinary(max), the CHARINDEX function will return a bigint value. Otherwise, it will return an int.
SELECT CHARINDEX('is', 'this is my string') -- returns 3
SELECT CHARINDEX('is', 'this is my string', 4) -- returns 6
SELECT CHARINDEX(' is', 'this is my string') -- returns 5