How to join two tables based on substring values of fields?

Question

I am having problem with sql. I want to join two tables, employee and class instructor. Condition is that employee is having unid column like \'u0871457\' where as class i

Answer 1

Oracle uses 1 as the base of its indexes, so substr('aaa',1,3) is equivalent to 'aaa'. You need to use 2 as the second parameter of substr in order to accomplish what you're attempting.

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Beyond that, you'd probably be better off only changing one side, if you can. If the prefix characters are consistent, you could do this:

SELECT e.name, i.name
FROM   employee e INNER JOIN instructor i ON REPLACE (e.id, 'u', '0') = i.id

This would potentially allow the database to use an index on instructor, which would not be possible with your solution.