Thread: How to build a query

On 01/20/2012 06:20 PM, JORGE MALDONADO wrote:
> I have to build a query at run-time which will contain a WHERE clause.
> There is a field in a table that has to be tested against several
> values but I do not know in advance how many values exist. For example,
>
> SELECT fld1, fld2, fld3 FROM tblTable
> WHERE fld1 = value[1] OR fld1 = value[2] OR fld1 = value[3]
>
> value[] is an array that contains all of the possible values that fld1
> may take but I do not know how many items such array has. A value of
> -1 in the array position indicates that it will not be taken into
> account. So, I need to traverse the whole array and include those
> values different from -1 in the WHERE clause. I can do a FOR...NEXT
> and concatenate the conditions getting only those values different
> than -1 but I wonder if this is a good approach; the query might grow
> depending on the number of valid values in the array. Please advice if
> there is a better way to build my query.
>
> Respectfully,
> Jorge Maldonado
SELECT columns
FROM tables
WHERE column1 in (value1, value2, .... value_n);

Mickg

On 21 January 2012 01:20, JORGE MALDONADO <jorgemal1960@gmail.com> wrote:
> I have to build a query at run-time which will contain a WHERE clause. There
> is a field in a table that has to be tested against several values but I do
> not know in advance how many values exist. For example,
>
> SELECT fld1, fld2, fld3 FROM tblTable
> WHERE fld1 = value[1] OR fld1 = value[2] OR fld1 = value[3]
>
> value[] is an array that contains all of the possible values that fld1 may
> take but I do not know how many items such array has. A value of -1 in the
> array position indicates that it will not be taken into account. So, I need
> to traverse the whole array and include those values different from -1 in
> the WHERE clause. I can do a FOR...NEXT and concatenate the conditions
> getting only those values different than -1 but I wonder if this is a good
> approach; the query might grow depending on the number of valid values in
> the array. Please advice if there is a better way to build my query.

Perhaps not what you want to hear, but if you had your values in a
separate table instead, you could do this:

SELECT fld1, fld2, fld3
FROM tblTable
INNER JOIN values ON tblTable.id = values.tblTable_id
WHERE values.value != -1;

But I suspect you know that.

--
Michael Wood <esiotrot@gmail.com>