Multiple Inner Join from The Same Table

Multiple INNER JOIN from the same table

You should specify different aliases for your tables . you are calling all of them m.

SELECT m1.MetalCode as 'Metal1', m2.MetalCode as 'Metal2',m3.MetalCode as 'Metal3'
FROM Item as k
INNER JOIN Metals AS m1 ON m1.metalID=k.metal1 
INNER JOIN Metals AS m2 ON m2.metalID=k.metal2
INNER JOIN Metals AS m3 ON m3.metalID=k.metal3
WHERE k.ItemID=?

MySQL: How do I join same table multiple times?

You need to use multiple LEFT JOINs:

SELECT 
    ticket.ticket_id,  
    a1.attr_val AS attr_val1,
    a2.attr_val AS attr_val2,
    a3.attr_val AS attr_val3
FROM ticket
    LEFT JOIN attr a1 ON ticket.ticket_id=a1.ticket_id AND a1.attr_type=1
    LEFT JOIN attr a2 ON ticket.ticket_id=a2.ticket_id AND a2.attr_type=2
    LEFT JOIN attr a3 ON ticket.ticket_id=a3.ticket_id AND a3.attr_type=3

Here is an example: SQL Fiddle.

INNER JOIN same table

I think the problem is in your JOIN condition.

SELECT user.user_fname,
       user.user_lname,
       parent.user_fname,
       parent.user_lname
FROM users AS user
JOIN users AS parent 
  ON parent.user_id = user.user_parent_id
WHERE user.user_id = $_GET[id]

Edit:
You should probably use LEFT JOIN if there are users with no parents.

Multiple join on same table

Try this;)

select r.phone, a.name as admin, re.name reseller, s.name as superadmin
from reseller_did r
join account a on a.id = r.admin_id
join account s on s.id = r.superadmin_id
join account re on re.id = r.reseller_id

SqlFiddle Result

Or

SELECT r.phone,
       MAX(CASE WHEN a.id = r.admin_id THEN a.name END) as admin,
       MAX(CASE WHEN a.id = r.reseller_id THEN a.name END) as reseller,
       MAX(CASE WHEN a.id = r.superadmin_id THEN a.name END) as superadmin
FROM reseller_did r
INNER JOIN account a 
ON a.id IN (r.admin_id, r.superadmin_id, r.reseller_id)
GROUP BY r.phone

This sql should thank to @sagi in this question Get multiple values from another table by different relations.

SqlFiddle Result

Inner Joining the same table multiple times

You need to use table aliases. You have mentioned the same table more than once in the from clause. The query is something like this:

SELECT b.BlankTypeCode, b.BlankCode, pa1.Amount, pa1.Type, p1.PurchaseDate, pa2.DatePaid
FROM Blank b
INNER JOIN Ticket t
ON b.BlankCode = t.Blank_BlankCode
INNER JOIN MCO_Blank mb
ON b.BlankCode = mb.Blank_BlankCode
INNER JOIN Purchase p1
ON  t.PurchaseID = p1.PurchaseID
INNER JOIN Purchase p2
ON mb.PurchaseID = p2.PurchaseID
INNER JOIN Payment pa1
ON t.PurchaseID = pa1.PurchaseID
INNER JOIN Payment pa2
ON mc.PurchaseID = pa2.PurchaseID
WHERE pa1.Status = "Paid";

I had to make a guess at which payment and purchase is intended for the aliases. These may not be correct in the from and where clauses.

Inner join multiple times on same table on same column

You want decode two value for rank (one for newrank and one for promoterrank ) then you should join tha table rank two time eg:

    SELECT A.*
      , B.rank as newrank
      , C.rank as promoterrank
      DATE_FORMAT(promotiontime, '%Y-%m-%dT%H:%i:%s0Z') 
    FROM promotions A 
    INNER JOIN ranks B ON A.newrank = B.id 
    INNER JOIN ranks C ON A.promoterrank = C.id
    WHERE agent='".$_POST['agent']."' ORDER BY id DESC

anyway you should avoid the use of php var in sql code .. (you are at risk for sqlinjection) so take a look at prepared statement and binding param

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