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Oracle / PLSQL: Extract the directory path from a full file path

Question: I have a string that contains the full path to a file. How can I extract the directory path from the string in Oracle?

For example, if I have a full file path as follows:

'c:\windows\temp\example.xls'

I want to retrieve the following:

'c:\windows\temp'

Answer: You can create a custom function in Oracle that will retrieve the directory path from the string value.

The following function called get_dir_path will extract the directory path. It will work with both Windows and UNIX system file paths.

CREATE OR REPLACE FUNCTION get_dir_path
   (p_path IN VARCHAR2)
   RETURN varchar2

IS
   v_dir VARCHAR2(1500);

BEGIN

   -- Parse string for UNIX system
   IF INSTR(p_path,'/') > 0 THEN
      v_dir := SUBSTR(p_path,1,(INSTR(p_path,'/',-1,1)-1));

   -- Parse string for Windows system
   ELSIF INSTR(p_path,'\') > 0 THEN
      v_dir := SUBSTR(p_path,1,(INSTR(p_path,'\',-1,1)-1));

   -- If no slashes were found, return the original string
   ELSE
      v_dir := p_path;
   END IF;

   RETURN v_dir;

END;

Once the above function has been created, you can reference this function in your SQL statement. For example,

SELECT get_dir_path('c:\windows\temp\example.xls')
FROM dual;

This SQL statement would return 'c:\windows\temp'.