Join two tables based on relationship defined in third table

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别那么骄傲
别那么骄傲 2020-12-24 01:36

I have two tables Activity and Action. One or more actions can be performed for an activity. And the relationships between Activity and Action is given in a third table call

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  •  旧巷少年郎
    2020-12-24 02:09

    This should do the trick

    SELECT Activity.ActivityText as Activity, Action.ActionText as ApplicableAction
    FROM ActivityAction
        INNER JOIN Activity
            ON ActivityAction.ActivityId = Activity.ActivityId
        INNER JOIN Action 
            ON ActivityAction.ActionId = Action.ActionId
    

    You should read up on JOINS in databases. Here is a good starting point:

    http://en.wikipedia.org/wiki/Join_%28SQL%29

    Basically what we have here is a many to many relationship between Activity and Action which is resolved by two one-to-many relationships using the a join table called ActivityAction.

    To get the required data back, we are joining ActivityAction to each one of the tables using the appropriate PK and FK columns and then choosing the string columns in the SELECT

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