Inner Join, SQL Function

Could someone explain me these line of code especially with the inner join and the select statement. Is this   f31122.wtan8 a reference to another table?  It will be greatly appreciated. Thank you.


 Declare @WORouting Table
(   WONbr float, 
    OpCode float, 
    OpCodeDesc nvarchar(100), 
    EstHours float, 
    ActHours float, 
    EmpNbr float, 
    EmpName nvarchar(100),
    WAITM float
 )


  Insert @WORouting
         (WONbr, 
          OpCode ,
          OpCodeDesc ,
          EstHours ,
          ActHours,
          EmpNbr ,
          EmpName ,
          WAITM 
 )
  Select wo.WONbr, 
         f3003.IROPSQ / 100, 
         f3003.IRDSC1, 
         f3003.IRRUNL, 
         sum(f31122.wthrw / 100), 
         f31122.wtan8,
         '',
         f3003.IRKIT
 
    from @WorkOrders wo
         inner join ps_prod.proddta.f3003 f3003 (nolock)
                 on wo.waitm = f3003.irkit  
                and ltrim(rtrim(f3003.IRMMCU)) = '308'
         inner join ps_prod.proddta.f31122 f31122 (nolock) 
                 on f3003.irkit = f31122.wtkit
                and f3003.iropsq = f31122.wtopsq
 group by wo.WONbr, 
         f3003.IROPSQ / 100, 
         f3003.IRDSC1, 
         f3003.IRRUNL, 
         f31122.wtan8,
         f3003.IRKIT

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yguyon28Asked:
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Phillip BurtonDirector, Practice Manager and Computing ConsultantCommented:
f31122 is a reference to the table ps_prod.proddta.f31122 (see line 36).

Within that table, there is a field called wtan8
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Vitor MontalvãoMSSQL Senior EngineerCommented:
f31122  is a table from ps_prod database and proddta schema (ps_prod.proddta.f31122).
What your script is doing is insert data in a table variable (@WORouting ) with information collected between another table variable (@WorkOrders)  and 2 tables (f3003 and f31122) where IRMMCU it's '308'.
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Vitor MontalvãoMSSQL Senior EngineerCommented:
From your other question:
----------------------------------------------------------------
-- Step 2: Fetch estimate/actual details for the work orders in question
--        F4801: work order header
--        F3003: routing master has operations and op desc
--                 (f4801.waitm = f3003.irkit
--                  f3003.IRDSC, f3003.IROPSQ / 100, f3003.RUNL est hours
--        F3112: summary work order routing -- not terribly useful because they want hours by person
--        F31122: individual hours by employee
--                f31122.wtkit = f3003.irkit, f31122.wtopsq = f3003.iropsq)
--                f31122.wthrw is actual hours
--                f31122.wtan8 = employee nbr (look up name in f0101)
--          
----------------------------------------------------------------
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yguyon28Author Commented:
I guess I'm having a hard time understanding this inner join

 from @WorkOrders wo
         inner join ps_prod.proddta.f3003 f3003 (nolock)
                 on wo.waitm = f3003.irkit  
                and ltrim(rtrim(f3003.IRMMCU)) = '308'
         inner join ps_prod.proddta.f31122 f31122 (nolock)
                 on f3003.irkit = f31122.wtkit
                and f3003.iropsq = f31122.wtopsq
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Vitor MontalvãoMSSQL Senior EngineerCommented:
What you don't understand in that INNER JOIN?
The INNER JOIN clause represents the relationship between tables. So for you assure the integrity of data between tables you need to give that information to the engine and it's what for the INNER JOIN is necessary.
NOLOCK means that the engine to not wait if the table is locked by other process so it allows dirty reads (data that can't be confirmed if it's changed during the SELECT).
LTRIM(RTRIM((f3003.IRMMCU)) is LeftTrim and RightTrim the values on the specified field so will return a value without leading and ending spaces. In that case the purpose is to accept '   308' or '308   ' as '308'.
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