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a column in a specific position?
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SPEAKER 1: Good question.
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Can we ask INSERT INTO the place a column in a certain position?
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There's a few ways of getting [? it-- ?] what I think you're asking here,
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so let me show you a few of those here.
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I'll come back to my computer, and let me pull up the syntax for INSERT INTO
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again.
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I will choose this, and I'll show it on the screen over here.
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So I'll say INSERT INTO some table given some columns.
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And notice how down below, I actually have [? values ?]
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to insert into those columns.
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I could, to your question, rearrange these values.
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So I might have this first value here is some value that goes into this column.
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The second column here is attached to that column.
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And that would rearrange the values I insert into those columns.
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If you're asking, though, if I can reorder the columns,
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that is up to [? CREATE ?] [? TABLE ?] and [? CREATE ?] [? TABLE ?] only.
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And in general, I encourage you not so much out of ordering of your columns,
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[? because ?] [? it ?] could be in any order whatsoever.
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But you could just rearrange your selection of columns
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here to insert the data you want to insert.
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OK, let's take one more question here.
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SPEAKER 7: What happens if one of the rows you're trying to insert
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violates a constraint on the table?
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SPEAKER 1: Yeah, so here we're inserting multiple rows.
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And if one actually violates some constraint,
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then we won't actually insert any of those rows.
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And this is because this insert is bundled inside
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of a transaction, which we'll learn more about later on in the course.
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Let's take another one.
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SPEAKER 8: I noticed that when you did SELECT [? star ?] FROM "collections,"
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that one of the acquired dates was just blank.
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It didn't say NULL.
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Is that because the CSV itself just had an empty value next to the comma?
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SPEAKER 1: Yeah, great observations.
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So let me try this again.
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So we can see the results of this [? SELECT. ?]
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I'll come back to my computer here, and let me show you again.
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If I say SELECT [? star ?] FROM "collections"
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semicolon, notice how this acquired column-- this acquired cell here, if I
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go back to my screen, it's just blank.
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But we saw before that if I [? selected ?] [? star, ?] I would have
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seen [? NULL ?] there if this value was truly [? NULL. ?] Well,
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it turns out one downside of importing from a CSV is that all of your data is
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imported initially as text.
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And if I have just a blank cell in my CSV,
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it won't be converted to [? NULL ?] automatically.
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I need to do that myself perhaps using an [? update ?]
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statement that we'll see in just a bit.
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So be wary of this if you do want to keep track of [? null ?] [? values ?]
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and so on.
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If you don't actually manually make this value a [? null, ?]
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it'll appear as just a blank value not a null,
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which is different in this respect.
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OK so here, we've seen how to insert not just one row, but multiple,
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and also how to import data from a CSV.
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When we come back, we'll see how to actually update our data altogether,
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and even delete it too.
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So come back in just a few and talk about how
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to delete data from our tables.
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And we're back.
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So we just saw how to insert some rows into our database,
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and also to import some data.
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But presumably, we also want to be able to delete some data from our table
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as well.
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You can imagine the MFA, the Museum of Fine Arts,
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maybe they're selling a piece of artwork, or maybe they've lost one,
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or maybe it was stolen.
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But either way, they want to remove the row from their table.
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Well, let's see here.
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We can go back to our schema with a table of artifacts and artwork
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that is inside of the MFA.
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Now if I want to delete a particular piece,
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you could visually think of it a bit like this.
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I could first identify that row I want to delete.
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Let's say it's Spring outing here.
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We've sold this piece.
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Well, I could visually just remove this row.
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So it's no longer there and shift the remaining ones up metaphorically.
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And it turns out that to do this in SQL, we
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have our very own statement we can use.
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This one reads DELETE FROM some table WHERE a condition is true.
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So we see our old friend WHERE back again.
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And WHERE is vitally important to this DELETE FROM.
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If I say DELETE FROM table with no WHERE,
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what do you think is going to happen?
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We might drop everything from our table, right?
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But if I instead say WHERE some condition is true,
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I can select the rows I want to delete and only delete those rows.
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So let's try this here.
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I'll try to delete some artwork from our collections table,
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for example, maybe we sold it and we want get rid of it.
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I'll come back to my computer over here, and I will open up our SQLite database.
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I'll say sqlite3 mfa.db.
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And now, I can type SELECT [? star ?] [? FROM ?] "collections,"
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and I see a few more items than last time now all inside of our table.
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But per the visual, I want to delete Spring outing,
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to remove it from this table.
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So what could I do?
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I could try DELETE FROM and then the table I want to delete from.
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