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  • Converting table columns to key value pairs

    - by TomD1
    I am writing a PL/SQL procedure that loads some data from Schema A into Schema B. They are both very different schemas and I can't change the structure of Schema B. Columns in various tables in Schema A (joined together in a view) need to be inserted into Schema B as key=value pairs in 2 columns in a table, each on a separate row. For example, an employee's first name might be present as employee.firstname in Schema A, but would need to be entered in Schema B as: id=>1, key=>'A123', value=>'Smith' There are almost 100 keys, with the potential for more to be added in future. This means I don't really want to hardcode any of these keys. Sample code: create table schema_a_employees ( emp_id number(8,0), firstname varchar2(50), surname varchar2(50) ); insert into schema_a_employees values ( 1, 'James', 'Smith' ); insert into schema_a_employees values ( 2, 'Fred', 'Jones' ); create table schema_b_values ( emp_id number(8,0), the_key varchar2(5), the_value varchar2(200) ); I thought an elegant solution would most likely involve a lookup table to determine what value to insert for each key, and doesn't involve effectively hardcoding dozens of similar statements like.... insert into schema_b_values ( 1, 'A123', v_firstname ); insert into schema_b_values ( 1, 'B123', v_surname ); What I'd like to be able to do is have a local lookup table in Schema A that lists all the keys from Schema B, along with a column that gives the name of the column in the table in Schema A that should be used to populate, e.g. key "A123" in Schema B should be populated with the value of the column "firstname" in Schema A, e.g. create table schema_a_lookup ( the_key varchar2(5), the_local_field_name varchar2(50) ); insert into schema_a_lookup values ( 'A123', 'firstname' ); insert into schema_a_lookup values ( 'B123', 'surname' ); But I'm not sure how I could dynamically use values from the lookup table to tell Oracle which columns to use. So my question is, is there an elegant solution to populate schema_b_values table with the data from schema_a_employees without hardcoding for every possible key (i.e. A123, B123, etc)? Cheers.

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