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so we could update it there.
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But somehow, we need to cascade it over to the [? artists ?] [INAUDIBLE] now
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this unidentified [? artist ?] [? through-- ?] I think we probably
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don't need it.
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SPEAKER 1: Yeah, so a good point here.
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We could actually probably change the created table to [? re-associate ?]
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an artist with some new artwork here.
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So let's visualize this.
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I go to my created table.
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And here the artist_id is currently 3, but I want it really to be 1.
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I want Li Yin to be associated with this piece called "Farmers working at dawn."
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So I could update the created table to instead of having 3 here have 1.
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Now, we see Li Yin created "Farmers working at dawn." [? And if ?]
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you're concerned about this Unidentified artist here,
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I think it's OK to have an artist in our table
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who may or may not have an item in collections.
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We'll say that's OK at least for now.
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So if we can update our associations between artists and collections
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like this, let's actually try to do that in our very own database here.
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I'll go back to my SQLite environment, and now, let me try to open it first.
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I'll use sqlite3 mfa.db.
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And now let me type .schema to show you [INAUDIBLE] the very same schema from
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before.
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So I want to update the artists association between Li Yin and "Farmers
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working at dawn."
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So let's say, I'll SELECT [? star ?] FROM "created," like this, semicolon.
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Here, I have my artist_ids and my collection_ids.
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I see that we have the Unidentified artist, id of 3,
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creating "Farmers working at dawn," with the id of 1 in our collection here.
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So now, let's try to update the artist who created this particular painting.
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Here, I have 3 associated with 1, but I want 1 associated with 1,
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where 1 is the id for Li Yin.
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And [? 1 ?] [? in ?] my collection id is the id for this artwork here.
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So let me try this.
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I'll say UPDATE "created" and SET, let's say, "artist_id"
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equal to some particular value.
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Well, what value should I set it to?
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I could try to set it to Li Yin's id, which we know is just 1.
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But let me try instead to use a [? subquery ?] here.
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Let me try to say parentheses, and then write some query to update this value.
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I'll say SELECT "id" from "artists" like this Enter again,
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WHERE the "name" equals Li Yin.
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And then let me close this [? subquery. ?] Well,
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if I try to run this query, what might Happen I'm updating the created table,
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I'm setting the artist_id equal to the id for Li Yin, but what I've forgotten
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is this WHERE to only choose some rows to update.
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[INAUDIBLE] not close it yet.
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I'll instead say WHERE, in this case, the "collection_id," the piece
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of artwork in our collection, is equal to [? while ?] the id
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for this painting.
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I'll say SELECT "id" from "collections," and then I'll
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say WHERE the "title" equals "Farmers working at dawn."
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Now, I'll close this [? subquery, ?] and hit semicolon.
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And here, we've seen our first example of an UPDATE query.
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I'm trying to update the artist_id column
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in created to be the id for Li Yin.
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I only want to do that though on the row where
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collection_id is equal to the id for this particular painting.
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[INAUDIBLE] change the attribution for.
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So now, I'll hit Enter.
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And if I SELECT [? star ?] FROM "created,"
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I should hopefully see in this case that the artist_id associated
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with this painting is 2 and also down below here is 1 as well.
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So I have Li Yin associated with now two paintings overall.
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So let's get a grasp on what this [? UPDATE ?] syntax really
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looks like in general.
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And for that, let's show the slide here.
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We have this [? UPDATE ?] [? keyword, ?] [? UPDATE ?] statement in SQL to take
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a table name and update the columns inside of it.
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I say UPDATE, then the name of the table I want to update,
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then I say SET some column equal to some value.
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I could if I wanted to have more than one column here.
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I could say maybe title and even maybe if we're
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talking about authors, authors over here, or even acquired date.
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I could update more than one column in my [? SET ?] [? portion ?] here.
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Then comes this WHERE portion, where some condition is true.
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I want to make sure I don't update all of my rows.
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I only update those where some condition is actually true.
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So this is your syntax for updating some columns.
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Let's say, if you want to change an artist's attribution
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or if you want to change a typo you've made.
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So let's see this now, not just in terms of changing
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artists and their attributions, let's see a use case for update
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where we've made some mistakes in our data.
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And let's say the museum decides to host some kind of event
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where people vote on their favorite piece of artwork,
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they kind of [? handwrite ?] or type it into some online form.
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Well, when I get back, a CSV of those responses,
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some Comma Separated Values, one line for each vote from our people
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who've attended this convention.
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Let's go back over here, and I'll show you that CSV.
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Let me go to my environment.
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And I'll type code mfa.csv to open this CSV that I already have.
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And here, actually, it's not called mfa.csv.
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It's called code votes.csv.
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And now here we can see, I have a table of one column
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that has several votes inside of it.
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Let's see, we have maybe 20 votes to be exact.
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So the first row is the header row.
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I have in this CSV, one column called title.
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