In SQL, we have tables containing individual rows. Tables have strict schemas that every row must obey; there are columns with types and other possible constraints: unique, not null, value checks or references to rows of other tables. Referential integrity lies at the heart of this data approach - guarantee that if row B1 of table B references row A1 of table A, referred row (A1) must exist; orphan rows are not allowed. If we want to delete A1 row, there are two options:
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Christine Cox became an organ donation campaigner after her brother died
1Why do I not like opera, then? I think it’s the singing, but it’s kind of complicated. Across all genres, I usually prefer instrumental music to song. When I was a kid, I also didn’t like musical movies, since I felt the music got in the way of telling the story. I’ve come around and enjoy musicals now, and furthermore I enjoy singing enough that I sing in a choir and like choral music, but I never developed a taste for lyrical singing, which is central to opera.
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