Cookin' with Ruby on Rails - May
Pages: 1, 2, 3, 4, 5, 6
Paul: OK. We've added a couple of columns. What's the big deal? I mean, other than that your scripts are database-independent and you don't have to remember how to write SQL scripts at all. Not that I'm saying that those aren't real nice, you know.
CB (grinning from ear to ear at this point): Remember, we're at Version 3 of the schema definition right now.
Figure 26.
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Our baseline is version 1, then we added the contributor_name column for Version 2, and then added the contributor_email for Version 3. So here comes the big deal...
Migrate back to Version 2.
Figure 27.
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Schema is automatically updated to the Version 2 structure.
Figure 28.
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Database structure is updated, without losing any of the remaining content.
Figure 29.
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Migrate back to Version 1, our baseline schema.
Figure 30.
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Schema is automatically updated,
Figure 31.
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as is the database, again without losing any of the remaining content.
Figure 32.
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