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by funnymony
972 days ago
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These examples reminded me one more issue: change in column selection, might change number of rows,
which means column addition/removal is so much riskier afair. > Not if distinct is the default. If that works for you, great, but let’s agree to disagree here. |
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Your mental model, if you will forgive the straw man, is that SELECT over multiple tables is conceptually equivalent to nested for-loops over each table, and the WHERE condition is an if-statement.
My mental model is that I'm working with sets. If yesterday I asked for the set of CITY,COUNTRY, and today I've changed that to the set of COUNTRY, then obviously the result set today is going to be much smaller. This is not a risk to me -- asking for a different set gives me a different set, I can't imagine being surprised by that.