Compare two delimited strings and return corresponding value in PL SQL - sql

Question

I have two columns with a hashtag delimited value, i.e. Email#Web#Telephone#SMS#MMS & 0#0#0#1#0 Note that each delimited value of the second column matches up with its corresponding delimited value in the first column, i.e. Email = 0, Web = 0, Telephone = 0, SMS = 1 etc.
Based on a parameter, I want to return the matching value of the second column. i.e. incoming param = Web#Telephone#SMS, thus the value that I want to return is 0#0#1.
This need to be done in PL SQL, and I have no clue where to start, which explains the lack of sample code.
Any help please?

Answer 1

There are a couple of very useful utility functions in an Oracle package called APEX_UTIL. (This package concerns Oracle Application Express aka APEX, but can be used anywhere). They are:
apex_util.string_to_table
apex_util.table_to_string
Using string_to_table you can convert the delimited string into a table of values:
declare
v_table apex_application_global.vc_arr2; -- This is the table type apex_util uses
begin
v_table := apex_util.table_to_string ('Email#Web#Telephone#SMS#MMS', '#');
end;
You now have an array with 5 elements ('Email', 'Web', 'Telephone', 'SMS', 'MMS');
You can do the same with the values string to get a table with elements ('0', '0', '0', '1', 0'). And you can do the same with the parameter to get a table with elements ('Web', 'Telephone', 'SMS').
You can then use PL/SQL logic to build a new array with elements for the values you need to return, i.e. ('0', '0', '1'). I have left this part to you!
Finally you can turn that back into a delimited string:
return apex_util.table_to_string (v_return_table, '#');

Answer 2

Firstly, you should normalize the table and have the attributes in different columns rather than delimited strings in a single column.
Anyway, you could do it in many ways using the techniques to Split comma delimited strings in a table
For example, using REGEXP_SUBSTR and CONNECT BY clause:
SQL> WITH DATA(attr, val) AS(
2 SELECT 'Email#Web#Telephone#SMS#MMS', '0#0#0#1#0' FROM dual
3 )
4 SELECT lines.COLUMN_VALUE,
5 trim(regexp_substr(t.attr, '[^#]+', 1, lines.COLUMN_VALUE)) attr,
6 trim(regexp_substr(t.val, '[^#]+', 1, lines.COLUMN_VALUE)) val
7 FROM data t,
8 TABLE (CAST (MULTISET
9 (SELECT LEVEL FROM dual CONNECT BY LEVEL <= regexp_count(t.attr, '#')+1
10 ) AS sys.odciNumberList ) ) lines
11 /
COLUMN_VALUE ATTR VAL
------------ --------------------------- ---------
1 Email 0
2 Web 0
3 Telephone 0
4 SMS 1
5 MMS 0
SQL>
Now, you can get the respective values for each attribute.
You could put the entire logic in a FUNCTION and return the corresponding values of each attribute and call the function in SELECT statement.
For example,
SQL> CREATE OR REPLACE
2 FUNCTION get_val_from_attr(
3 attr_name VARCHAR2)
4 RETURN NUMBER
5 IS
6 var_val NUMBER;
7 BEGIN
8 WITH DATA(attr, val) AS
9 ( SELECT 'Email#Web#Telephone#SMS#MMS', '0#0#0#1#0' FROM dual
10 ),
11 t2 AS
12 (SELECT lines.COLUMN_VALUE,
13 trim(regexp_substr(t.attr, '[^#]+', 1, lines.COLUMN_VALUE)) attr,
14 trim(regexp_substr(t.val, '[^#]+', 1, lines.COLUMN_VALUE)) val
15 FROM data t,
16 TABLE (CAST (MULTISET
17 (SELECT LEVEL FROM dual CONNECT BY LEVEL <= regexp_count(t.attr, '#')+1
18 ) AS sys.odciNumberList ) ) lines
19 )
20 SELECT val INTO var_val FROM t2 WHERE attr = attr_name;
21 RETURN var_val;
22 END;
23 /
Function created.
Let's call the function:
SQL> SELECT get_val_from_attr('Email') FROM dual;
GET_VAL_FROM_ATTR('EMAIL')
--------------------------
0
SQL> SELECT get_val_from_attr('SMS') FROM dual;
GET_VAL_FROM_ATTR('SMS')
------------------------
1