Python for .NET Developers Transcripts
Chapter: Database access and ORMs in Python
Lecture: Concept: Querying data
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Once you have some data in the database well, of course you want to get it back and you want to query it, and slice it, and dice it
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and group it, and all the cool stuff. So, here is our function, a simplified version that says given a style, a string, we want to get all the guitars
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that have a style that match that string. So we're going to go and say create a session. Again, bare metal stuff, just SQLAlchemy types
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not our cool, higher level version. And we say ctx.session.query(Guitar) and then we're going to put the where clause
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basically the filter clause is guitar.style == style. It's really cool how these are called descriptors
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these columns are able to, at run time, be one thing and then at, kind of, evaluation time like this be yet another.
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So that's a pretty cool language trick and then if we were calling list and wrapping it we could also do an equivalent thing
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by saying .all and that'll turn into a list. Basically, get all the stuff back, and then just to be safe, we're wrapping it in a list
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at the bottom here and we're turning that. So, this is how we go and query the database. We're not doing our order by, but you saw that of course
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if we wanted to, we could order these easily. Once we run this query, if we had echo term to true
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which could look at our database tools, you would see that we would issue a SQL command over to the database.
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select * from guitars where style = @style. Pretty cool, huh? Couple things to note: First of all it's using parameters
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so SQL injection attack and little Bobby Tables not a problem with SQLAlchemy, which is great. The other one is it doesn't technically say
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select . It specifically lists out everything that it expects. Get a slightly different more complicated-looking output, but
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effectively, there's like a simplified version of what happens when we run this code here.