Re[2]: [SQL] Please help: How to determine largest of two numbers in a query?

Hello David,

giovedì, 3 dicembre 98, you wrote:

DH> My $.03 worth, without really knowing what these values represent:

DH> There is no such "standard" query that can conditionally select between two
DH> columns. Fortunately PostgreSQL will allow you to create function - of one
DH> does not already exist.

DH> The function would be something like:
DH> greater_int(integer a, integer b)
DH> It takes two integers arguments and returns the greater integer.

DH> Then you do something like:

DH> CREATE VIEW myview AS
DH> SELECT yyymmdd, key, greater_int(value1, value2) FROM mytable;

DH> Or just do the SELECTs directly.

DH> This may not be the most efficient way to accomplish your goal. I would also
DH> take a good look at may table design. Value1 and value2 MAY be a repeating
DH> group and you may want to normalize a little more. Or not.

DH> Greg Youngblood wrote:

>> I have a table with the following structure:
>> yyyymmdd int4
>> key char(16)
>> value1 int4
>> value2 int4
>>
>> with the following sample data:
>> yyyymmdd key value1 value2
>> 19981201 hello 32 16
>> 19981201 bye 29 64
>> 19981202 hello 16 20
>> 19981202 bye 23 13
>>
>> What I need is to select the greatest between value1 and value2, so the
>> answer would be:
>> yyyymmdd key value
>> 19981201 hello 32
>> 19981201 bye 64
>> 19981202 hello 20
>> 19981202 bye 23
>>
>> I can do this via ODBC using access by creating a column which is defined as
>> IF(value1>value2,value1,value2) but that doesn't work in psql.
>>
>> How can I make this work in psql?
>>
>> Thanks
>> Greg

PostgreSQL has already these built-in funcions (those used on
aggregate MIN/MAX):

int2 |int2larger |int2 int2 |larger of two
int2 |int2smaller |int2 int2 |smaller of two
int4 |int4larger |int4 int4 |larger of two
int4 |int4smaller |int4 int4 |smaller of two
int8 |int8larger |int8 int8 |larger of two
int8 |int8smaller |int8 int8 |smaller of two

exemple:

SELECT int4larger(3,10)
int4larger
----------
10
(1 row)

-Jose'-