sql - Query returns no records -

hello making schema purchasing orders these orders can ordered user , received user.

so created below schema.

schema

the issue when userid column in purchaseorders , deliveries tables has different values query returns no records.

query

select   dbo.users.firstname,   dbo.users.lastname,   dbo.purchaseorders.purchaseorderdate,   dbo.deliveries.expecteddeliverydate,   dbo.deliveries.actualdeliverydate dbo.purchaseorders inner join dbo.users   on dbo.purchaseorders.userid = dbo.users.userid inner join dbo.deliveries   on dbo.purchaseorders.purchaseorderid = dbo.deliveries.purchaseorderid   , dbo.users.userid = dbo.purchaseorders.userid   , dbo.users.userid = dbo.deliveries.userid 

you need 2 different joins users. need learn use table aliases:

select pu.firstname purchase_firstname, pu.lastname purchase_lastname,        du.firstname delivery_firstname, du.lastname delivery_lastname,        po.purchaseorderdate,        d.expecteddeliverydate, d.actualdeliverydate dbo.purchaseorders po join      dbo.deliveries d      on po.purchaseorderid = d.purchaseorderid join      dbo.users pu      on p.userid = pu.userid join      dbo.users du      on d.userid = du.userid; 

your query returns no records because of condition:

  , dbo.users.userid = dbo.purchaseorders.userid   , dbo.users.userid = dbo.deliveries.userid 

this means dbo.purchaseorders.userid = dbo.deliveries.userid. so, if not true, no records match condition.