将三个SQL语句合并为一个

Question

I have looked at combining two tables into one statement with SQL, but the examples I find online for combining 3 or more look to complicated for me to grasp...

I am looking to combine 3 statements into one, i believe it should be possible. Here is some pseudo code for what I am trying to achieve.

Select tagId from tags where tagName = "test"
->
Select photoId from photoTags where tagId = (tagId from previous statement)
->
Select * from pictures where id = (photoId from previous statement)

How can I combine this into one statement? I have a simple understanding of using JOIN but I don't understand multiple joins.

Is what I am trying to accomplish even possible as one statement?

Thanks

Answer 1

You should be able to access the pictures using such query:

SELECT p.* 
FROM pictures p
    INNER JOIN photoTags pt on pt.photoId = p.id  -- Join tables pictures and photoTags
    INNER JOIN tags t on pt.tagId = t.tagId -- join tables photoTags and tags
WHERE t.tagName = "test"

It selects all columns from pictures table and filters the data by tagName="test"

Answer 2

SELECT T.TagId,PT.PhotoId,P.* FROM Tag T 
JOIN photoTags PT On PT.tagId =T.TagId
JOIN pictures P On P.Id=PT.PhotoId
WHERE T.TagName="test"

Answer 3

Try This

SELECT p.* 
FROM pictures p
    JOIN photoTags pt on pt.photoId = p.id 
    JOIN tags t on pt.tagId = t.tagId 
WHERE t.tagName = "test"