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copied!<p>I think you need to join before you filter and use just one query:</p> <pre><code># Get all the versions of a single course. versions = Curriculum_Version.query.join(Curriculum_Version.course).filter( Course.course_code == "PIP-001").all() </code></pre> <p>Otherwise sqlalchemy will not know to use the relationship before filtering.</p> <p>If you just specify a filter then sqlalchemy does not know to perform a join and you end up with sql similar to this:</p> <pre><code>SELECT curriculum_versions.* FROM curriculum_versions, courses WHERE courses.course_code = "PIP-001" </code></pre> <p>Which does not make a whole lot of sense but is valid SQL. When you use a join it leverages the filter against the correct table like this:</p> <pre><code>SELECT curriculum_versions.* FROM curriculum_versions JOIN courses ON curriculum_versions.course_id = courses.id WHERE courses.course_code = "PIP-001" </code></pre> <p>Note that sqlalchemy knows to use the condition <code>curriculum_versions.course_id = courses.id</code> because you pass in <code>Curriculum_Version.course</code> to <code>query.join()</code> and you specified that relationship on your <code>Curriculum_Version</code> class as the course property and it automatically knows to use the only foreign key available between the <code>curriculum_versions</code> and <code>courses</code> tables (which you also had to specify on the <code>curriculum_versions.course_id</code> column).</p> <p>You can read more about joins here: <a href="http://docs.sqlalchemy.org/en/rel_0_7/orm/tutorial.html#querying-with-joins" rel="nofollow">http://docs.sqlalchemy.org/en/rel_0_7/orm/tutorial.html#querying-with-joins</a></p>

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