Re: How do I extract ONE particular field, when multiple table contain the same field name?

olle(dot)wijk(at)systecon(dot)se (Olle Wijk) wrote in message news:<6baa8767(dot)0109120106(dot)67f94cf5(at)posting(dot)google(dot)com>...
> Hi,
>
> I am pretty new att using SQL-quires, could anyone help me with this
> one:
>
> I want to do the following SQL-query:
>
> Select XID, DENOM, PRICE, FRT, CTID From XItem xi, Category c Where
> xi.System=1 and xi.Category=c.Index
>
> the problem is that the field 'DENOM' is present in both table 'XItem'
> and
> 'Category' (it is a text description field where you explain whatever
> you
> want). Therefore I get the following complaint when I run the query:
>
> Error msg: "The specified fiel 'DENOM' could refer to more than one
> table listed
> in the FROM clause of your SQL-statement"
>
> The DENOM-field I actually want is the one belonging to the
> XItem-table.
> I would most appreciate if someone could give me a hint how to alter
> the
> SELECT-statement above so that it does what I want.
>
> Regards
>
> /olw

When joinning tables, as you did, it's hardly recommended using
aliases, as you did too. (XItem <=> xi and Category <=> c). These
aliases can be used in all the SELECT statement including WHERE
clause, as you did again :), and SELECT clause. So, to refer to the
DENOM field from the table XItem, you should write :
xi.DENOM instead of DENOM alone. Your SELECT statement will be :

Select XID, xi.DENOM, PRICE, FRT, CTID From XItem xi, Category c
Where
xi.System=1 and xi.Category=c.Index

Notice than if you don't want to use aliases (what a wrong idea !),
you can write like the following :

Select XID, XItem.DENOM, PRICE, FRT, CTID From XItem, Category Where
XItem.System=1 and XItem.Category=Category.Index

Just some remarks about writing SQL statement.
it's preferabled (in my point of view) to :
- write key words (like SELECT, FROM, WHERE, ...) in upper case
- go to the next line when you change of key word
- always use aliases
- keep always the same alias for the same table in all the queries
- write the fields in lower case
- write the first lettre of a table name in upper, the rest in lower
case
- use a "_ID" suffixe to the field name when it correspond to the
primary key of another table
- name "ID" the primary key of a table

I would write your sql statement like :

SELECT xi.ID, xi.denom, xi.price, xi.frt, cat.ID
FROM XItem AS xi, Category AS cat
WHERE xi.system = 1 AND xi.category_ID = cat.ID;

good luck
Yoann