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    <p>Only with dynamic SQL. It is also possible to left join many different tables and use CASE based on type, but the tables would be all have to be known in advance.</p> <p>It would be easier to recommend an appropriate design if we knew more about what you are trying to achieve, what your design currently looks like and why you've chosen that particular table design in the first place.</p> <pre><code>Say you have a table of foods: id INT foodtype VARCHAR(50) (right now it just contains 'hotdog' or 'hamburger') name VARCHAR(50) Then hotdogs: id INT length INT width INT Then hamburgers: id INT radius INT thickness INT </code></pre> <p>Normally I would recommend some system for constraining only one auxiliary table to exist, but for simplicity, I'm leaving that out.</p> <pre><code>SELECT f.*, hd.length, hd.width, hb.radius, hb.thickness FROM foods f LEFT JOIN hotdogs hd ON hd.id = f.id AND f.foodtype = 'hotdog' LEFT JOIN hamburgers hb ON hb.id = f.id AND f.foodtype = 'hamburger' </code></pre> <p>Now you will see that such a thing can be code generated (or even for a very slow prototype dynamic SQL on the fly) from <code>SELECT DISTINCT foodtype FROM foods</code> given certain assumptions about table names and access to the table metadata.</p> <p>The problem is that ultimately whoever consumes the result of this query will have to be aware of new columns showing up whenever a new table is added.</p> <p>So the question moves back to your client/consumer of the data - how is it going to handle the different types? And what does it mean for different types to be in the same set? And if it needs to be aware of the different types, what's the drawback of just writing different queries for each type or changing a manual query when new types are added given the relative impact of such a change anyway?</p>
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    1. POMYSQL join tables based on column data and table name
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    1. USCade Roux
    1. USCade Roux
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    1. COThnks for the replay.... I like the union solution thought im not sure hot to implement it. So heres the detail. Student makes a request on some tipe of letter, on table "request", the data of the student and the "letter type" are saved. Theres 10 different posible values for the "letter type". So I have 10 tables with the specific letter type name, like.. Table recomendation, Table transfer, So I wanted A way to do all the SELECT on 1 query Based on the student letter, to call the specific table and get the data from it.
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    2. CO@user1052347 Bill Karwin gives several links to designs. Ultimately, because the associated data for each type is different, an actual "SELECT *" is not likely to work, since the auxiliary information in each of the tables is going to be different. You need to decide what you want the result set to look like. At that point, you can code by hand (or even potentially code generate/dynamic SQL - thus somewhat eliminating the maintenance problems with changing schemas). I will give an example in my answer.
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