Re: SQL 101

>From: "Robert Manning" <robert.m.manning@xxxxxxxxx>
>To: "Tyrone Baseck" <tyrone_bak@xxxxxxxxxxx>
>CC: squirrel-sql-users@xxxxxxxxxxxxxxxxxxxxx
>Subject: Re: [Squirrel-sql-users] SQL 101
>Date: Tue, 20 Mar 2007 17:40:42 -0400
>
>On 3/20/07, Tyrone Baseck <tyrone_bak@xxxxxxxxxxx> wrote:
>>I will get help from the DBA on that query listed earlier.  The one listed
>>below works.  Now, what is it doing:
>>
>>select * from MGD_REQ_HOLDG m inner join AUTH_REQ_ITEM_HDR a on
>>m.REQ_ITEM_HDR_ID = a.REQ_ITEM_HDR_ID
>>where a.auth_req_id
>>
>>Do I need to change the MGD_REQ_HOLDG in the first line to look at another
>>table?
>
>You are saying join tables MGD_REQ_HOLDG and AUTH_REQ_ITEM_HDR by
>matching records where the field REQ_ITEM_HDR_ID in both tables is
>equal.  If you need columns from other tables, then you would add them
>to your join.  The where clause :
>
>where a.auth_req_id
>
>is incomplete.  You should give a value for auth_req_id like :
>
>where a.auth_req_id = 42
>
>or not include a where clause at all (which could be quite a large
>number, depending on the data)
>
>>
>>What is the lower case "m" and "a" for?
>
>Table aliases are more convenient than using the entire table name.
>
>>
>>Why do you need to add a "a" to a.REQ_ITEM_HDR_ID instead of doing it
>>without the "a"?
>
>Both tables apparently have a column called REQ_ITEM_HDR_ID, so the
>database doesn't know which one you are referring to.  The table
>aliases "m" and "a" tell it which one you mean.
>
>
>Rob

Oh!! So the a.REQ_ITEM_HDR_ID can be inputted as the following:  
AUTH_REQ_ITEM_HDR.REQ_ITEM_HDR_ID

No answer needed on that comment.

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