How to make first letter uppercase

By using INITCAP function it is possible to make first letter of word UPPERCASE

example

select INITCAP('sample initcap') from dual

result: Sample Initcap

How to find a word with different endings in the string

SELECT

REGEXP_SUBSTR('I have earned 100 dollars today ','earn((ing)|(ed))')

FROM dual;

result : earned

If you change the string

SELECT

REGEXP_SUBSTR('I have been earning 100 dollars today ','earn((ing)|(ed))')

FROM dual;

result: earning

How to add first name first letter to last name name

By using regular expression replace it is possible to add first letter of name to the beginning of the last name.

SELECT LOWER(regexp_replace('Lucky, Edy E', '(.+)(, )([A-Z])(.+)','\3\1', 1, 1))

  FROM DUAL;

Result : elucky

How to find alphabetic characters (a-z, A-Z)

By using '[[:alpha:]]' with regular expressions it is possible to find 
alphabetic characters. By adding {3} at the end we limit the length of matching 
alphabetic characters.


Select * from test_table where REGEXP_LIKE(test_column, '[[:alpha:]]');

Select * from test_table where REGEXP_LIKE(test_column, '[[:alpha:]]{3}');

How to find alphanumeric characters (a-z, A-Z, 0-9)

By using '[[:alnum:]]' with regular expressions it is possible to find 

alphanumeric characters.By adding {3} at the end we limit the length of 

matching alphanumeric characters.

Select * from test_table where REGEXP_LIKE(test_column, '[[:alnum:]]');

Select * from test_table where REGEXP_LIKE(test_column, '[[:alnum:]]{3}');

How to find repeating substring within string

By using regular expression it is possible to find repeating substring within string

select 

        regexp_replace('telltell','^(.+?)\1*$','\1') sub_str

  from  dual

How to find first character of string

By suing SUBSTR  it is possible to find it.

 select SUBSTR ('testing est for test', 1, 1) from dual

resul:t