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I was reading about App Engine on wikipedia and came across some GQL restrictions:
JOIN is not supported
can SELECT from at most one table at a time
can put at most 1 column in the WHERE clause
What are the advantages of these restrictions?
Are these restrictions common in other places where scalability is a priority?
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A GQL query returns zero or more entire entities, projected entities, or keys of the requested kind. Every GQL query always begins with SELECT * , SELECT __key__ or SELECT <property list> , where property is a comma delimited list of one or more entity properties to be returned from the query.
The Python Datastore API provides two classes for preparing and executing queries: Query uses method calls to prepare the query. GqlQuery uses a SQL-like query language called GQL to prepare the query from a query string.
The datastore that GQL talks to is:
One reason to have a database like this is to have a very high performance database that you can scale across hundreds of servers.
GQL is not SQL it is SQL-like.
Here are some references:
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