Need help on getting the column names of Tabletype

Question

I have a table Mapping with the following values: This Mapping table contains the table names (in Tabname) and the column names(colname) of various tables and values(ValuesTobeFilled) for the columns.
I have to insert into the tables present in the Tabname field with the values present in the ValuesTobeFilled in the columns present in the Colname field.
Note: The Mapping table need not contain all the columns of the base table. The columns that are not present can be filled with null. And this mapping table is not fixed i.e. rows can be inserted/deleted frequently.
Sample values in mapping table:
Tabname                        Colname        ValuesTobeFilled
sample_items     Eno     Corresponding Expression to get the values from XML input
sample_items     Ename     Corresponding Expression to get the values from XML input
XXX     YYY     Corresponding Expression to get the values from XML input
Before filling in the actual tables, I have to store the entire data temporarily and I have used a tabletype declared as follows:
TYPE T_sample_items IS TABLE OF sample_items%ROWTYPE INDEX BY BINARY_INTEGER;
l_sample_items T_sample_items;
Where the table sample_items have the following columns:
•     Eno
•     Ename
•     Eaddress
•     Eemail
So, the tabletype should be filled as:
Eno     Ename     Eaddress     EEmail
1     XXX     -     -
I have declared a cursor to select the values from mapping table and I need to fill in the ValuesTobeFilled values to the corresponding table.
CURSOR c_xpath (c_tname mapping.TABNAME%type)
IS
select * from mapping where tabname = c_tname;
CURSOR c_tables
IS
SELECT DISTINCT TABNAME FROM mapping;
FOR crsr IN c_tables
LOOP
p_tname := CRSR.TABNAME;
FOR csr IN c_xpath(p_tname)
LOOP
IF l_xml_doc.EXISTSNODE(CSR.XPATH_EXP) = 1
THEN
l_node_value := l_xml_doc.extract(CSR.XPATH_EXP).getStringVal(); -- This is the value to be stored in the corresponding column
ELSE
     l_node_value := NULL;
END IF;
IF CSR.COLUMN_NAME = ‘eno’
THEN
     l_sample_items(1).eno := l_node_value;
ELSIF CSR.COLUMN_NAME = ‘ename’
THEN
     l_sample_items(1).name := l_node_value;
END IF;
END LOOP;
END LOOP;      
And I need to eliminate hard coding while comparing the column names (in the following piece of code) as the Mapping table values are subject to insertion/deletion:
IF CSR.COLUMN_NAME = ‘eno’
THEN
     l_sample_items(1).eno := l_node_value;
ELSIF CSR.COLUMN_NAME = ‘ename’
THEN
     l_sample_items(1).ename := l_node_value;
END IF;
I need to insert the values directly into the tabletype without this hardcoding. Please suggest me ways to compare the mapping table values with the field (column) names of the tabletype. If it is not possible using tabletype, please suggest any other ways of fixing the problem.
Many thanks,
Gopi

Answer 1

I take it this isn't going to be a serious production system at the end of the day?
Storing metadata in tables for extraction and insertion of data is just wrong in so many ways. It smells heavily of Entity Attribute Value modelling, which is the most wrong way to use a relational database and is known to have major performance implications and be liable to bugs and issues. The idea that EAV modelling allows for 'generic' databases where new data items can be added flexibly later on without having to change code is usually justified with an excuse of "it means we don't have to update all our tables when we want a new column" which is easily countered with "if you're adding a single column a good relational design wouldn't require you to add it to more than one table anyway in most cases".
Just what exactly are you trying to do and why? There has to be a better way.