csnotes/cst363/lec/lec6.md

lec6

Lab activity

This lecture features a lab activity in the lab/ directory named: courses-ddl.sql with instructions in simple-joins-lab.pdf.

• Note: Just make sure to read in courses-ddl.sql first then courses-small.sql second otherwise there will be random errors.(I'm not taking responsibility for that garbage so don't flame me)

Natural Joins

Natural Joins: allows us to join tables while getting rid of duplicate columns automatically.

Form:

select columns_[...] from tableLeft natural join tableRight

While there is no need to write extra where statements there is also the issue where there may be accidental matches since attributes are dropped. This implies that if two tables have attributes with the same field name, then only one will be returned in the resulting table.