Question

I have a dynamic list of categories, which is retrieved from mySQL. When the user is clicking on a category, it loads images for that specific category from the DB. This is the function that does it:

function getImages($categoryID)
{
return json_encode(select("SELECT * FROM images WHERE categoryID=$categoryID"));
}

Now I also want to retrieve also the category name again from the “categories” table (to include the name of the selected category in other part of the page). I tried to do this:

function getImages($categoryID)
{
return json_encode(select(
        "SELECT categories.categoryName, images.imageFileName, images.imageHeader 
        FROM images JOIN categories 
        ON categories.categoryID = images.categoryID 
        WHERE categoryID=$categoryID"));
}

but that didn’t work, now I don’t even get the images.

How can it be done?

Answer 1

In your WHERE clause, categoryID is ambiguous.

WHERE categoryID=$categoryID

Since you have two tables with categoryID, you need to identify which one the WHERE should be looking at.

WHERE categories.categoryID=$categoryID

To make life easier for yourself, you might want to consider aliasing your tables, like this:

SELECT c.categoryName, i.imageFileName, i.imageHeader 
FROM images i
JOIN categories c ON c.categoryID = i.categoryID 
WHERE c.categoryID=$categoryID

Also, which language are you developing in? If this is a web app, you might want to consider escaping $categoryID to protect against SQL injection.