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A foreign key is a column or columns of data in one table that refers to the unique data values -- often the primary key data -- in another table. Foreign keys link together two or more tables in a ...

At my company every foreign key has a NOT NULL constraint on it, and if it really needs to be null in some cases, a default value is assigned (like 999999) and given a row in the referring table like ...

When I am working with an Oracle database, I still find myself using SQL*Plus for many quick and dirty database queries. In particular, I often look up constraints in SQL*Plus. In this post, I look at ...