create or replace FUNCTION lcs(    
  in_str1 IN VARCHAR2,    
  in_str2 IN VARCHAR2    
) RETURN VARCHAR2    
IS    
  TYPE numbers_array IS TABLE OF PLS_INTEGER INDEX BY PLS_INTEGER;    
  TYPE Array2D IS TABLE OF numbers_array INDEX BY PLS_INTEGER;    
  c_l1                  SIMPLE_INTEGER := 0;    
  c_l2                  SIMPLE_INTEGER := 0;    
  p_matrix              Array2D;    
  p_c1                  NCHAR(1);    
  p_c2                  NCHAR(1);    
  endingIndex           SIMPLE_INTEGER := 0;    
  maxlen                SIMPLE_INTEGER := 0; --lcs  
  l_check               SIMPLE_INTEGER := 0; --check if there are any matching characters between the 2 strings  
BEGIN    
        
    IF in_str1 IS NULL OR in_str2 IS NULL THEN    
        RETURN NULL;    
    ELSIF c_l1 > c_l2 THEN    
        RETURN lcs( in_str2, in_str1 );    
    END IF;  
      
    --check if there are any matching characters; if none found, RETURN NULL  
    --@todo: might consider removing the whitespaces before making the comparison  
    SELECT  
        COUNT(1)  
    INTO  
        l_check  
    FROM  
    (  
        SELECT in_str1 initial_string, TRANSLATE ( in_str1, in_str2, '#' ) output_string FROM dual  
    )  
    WHERE  
        initial_String = output_string  
    ;  
    IF l_check = 1  
    THEN  
        RETURN NULL;  
    END IF;  
      
    c_l1 := LENGTH(in_str1);    
    c_l2 := LENGTH(in_str2);    
        
    --initialize all cells of lookup table to 0  
    FOR i IN 1..c_l1  
    LOOP  
        FOR j IN 1..c_l2  
        LOOP  
            p_matrix(i)(j) := 0;  
        END LOOP;  
    END LOOP;  
  
    FOR i IN 1..c_l1    
    LOOP    
        --Check if the length of current position + length of remaining string <= max length found, exit  
        p_c1 := SUBSTR( in_str1, i, 1 );  
        FOR j IN 1..c_l2    
        LOOP    
            p_c2 := SUBSTR( in_str2, j, 1 );    
            --if current character of X and Y matches    
            IF p_c1 = p_c2    
            THEN    
                if p_matrix.exists ( i-1 ) and p_matrix ( i-1 ).exists ( j-1 )   
                then  
                    p_matrix ( i )( j ) := p_matrix ( i-1 )( j-1 ) + 1;   
                else   
                    p_matrix ( i )( j ) := 1;  
                end if;  
                  
                IF p_matrix(i)(j) > maxlen    
                THEN    
                    maxlen := p_matrix(i)(j);    
                    endingIndex := i;  
                END IF;  
                /*  
                IF (c_l1 - i) < maxlen  
                THEN  
                    RETURN SUBSTR(in_str1, endingIndex - maxlen + 1, maxlen);    
                END IF;  
                */  
            END IF;    
        END LOOP;    
    END LOOP;    
  
    RETURN SUBSTR(in_str1, endingIndex - maxlen + 1, maxlen);    
    
END lcs;

select lcs('WIKIMEDIA', 'REMEDYA') from dual

select lcs('WIKIMEDIA', 'REMEDYA') from dual