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POMYSQL - How to check if a user is following another user, potentially through a subselect?
 

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  1. POMYSQL - How to check if a user is following another user, potentially through a subselect?
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    <p>I'm fetching a list of activities (activities) and using a left join to grab the user data (users) who created the activity. Within my application users have the ability to follow one another.</p> <p>This is my current query, which grabs all activities not posted by yourself ($user_id)</p> <pre><code>SELECT activities.id, activities.user_id, users.id, users.name FROM activities LEFT JOIN users on activities.user_id = users.id WHERE users.id != $user_id </code></pre> <p>Aside from the activities + users tables, I have a another table in my application called followers:</p> <pre><code>followers id | user_id_1 | user_id_2 | followed_back 1 1 3 1 2 2 3 0 3 3 1 1 </code></pre> <p><strong>I need to check whether you ($user_id) have followed a particular user joined to each activity and perhaps call this new field "user_followed" which represents a true/false/null value?</strong> </p> <p>For example, I'm user_id = 1. Based on the above table, this means I have followed user_id 3. When an activity is fetched and user_id 3 is joined / responsible, the new field "user_followed" would be true.</p> <p>Therefore, I think I'd need to incorporate another SELECT query, checking if the user is being followed:</p> <pre><code>(SELECT * FROM followers WHERE user_id_1 = $user_id AND user_id_2 = users.id ) </code></pre> <p>I'm just largely unsure of how to incorporate this into my initial query and create a new field representing yes or no. Any help would be much appreciated!</p>
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    1. USDanny
    1. USDanny
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      1. POMYSQL - How to check if a user is following another user, potentially through a subselect?
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    1. COyour query does not make sense at all. Your example is wrong because columns 2 and 3 should have the same values, this is, according to the query you had written. The join condition is **activities.user_id = users.id**, hence columns 2 and 3 of table followers will have the same values making the initial query useless... had you even tried it before posted it here?
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    2. COI'm unsure what my second query should be. I just wrote it, because by itself it checks whether a follower exists by returning a row or not. I'm asking this question because I don't know how to do it...
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      1. POMYSQL - How to check if a user is following another user, potentially through a subselect?
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    3. COwell your first query doesn't work. I already explained you why.
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