To retrieve a list of tables in particular schema, you can use the following SQL statement:
SELECT PACKAGE_ID, OBJECT_NAME, CDATA FROM "_SYS_REPO"."ACTIVE_OBJECT" where object_type_id = 'hdbtable';
You will have all the field names of the table in CDATA column (though it will take a bit or parsing).
As Lars pointed out, once you have the table name and field information, you will have to write a procedure which can find an input search term.