mysql union或仅加入一个查询

Question

I need to find a better way to get the discount for each article price in our web shop depending on which pricelist or pricelist/discount list a customer has. I think this is possible to do in just one query instead of the 5 I have today, but I really do not know where to start.

All our customers have a pricelist and some have both pricelist and one extra discount list. Today we have about 25 different pricelists and about 100 extra discount lists. All the pricelists are structured in the same manner; they have a price group and a discount in percent.

For example pricelist 01 could look like

A 20

B 35

C 20

The extra discount list is structured in a different manner and can have a fixed price or percentage. It also has three different priority levels: discount based on the article code (has priority 1), based on category (has priority 2) and based on price group (has priority 3).

Discount list 0013 could look like:

In the article tab

PL-2344-444 40 (%)

P-0455-23 200 (SEK)

In the category tab

C12 50 (%)

N12 35 (%)

Today I have three different queries to see if I get a hit in the discount list:

First I check to see if I get a hit in priority 1: (FIXED returns f and PERCENTAGE r)

SELECT DISCOUNT, FIXED, PERCENTAGE FROM PUPRIREG 
WHERE ARTCODE = 'JO-23455' AND DISCOUNTLIST = '0013'

If the above returns 0, I do the second query, priority 2:

SELECT DISCOUNT, FIXED, PERCENTAGE FROM PUPRIREG 
WHERE CATEGORY = 'C15' AND DISCOUNTLIST = '0013'

And the last one priority 3:

SELECT DISCOUNT, FIXED, PERCENTAGE FROM PUPRIREG 
WHERE PRICEGROUP = 'F' AND DISCOUNTLIST = '0013'

If none of the extra discount lists returns 0 I get the discount from the pricelist

SELECT DISCOUNT FROM PUPRIREG WHERE PRICELIST = '01' AND PRICEGROUP = 'F'

I call the function like follows $discount = discount($articlecode, $category, $pricegroup);

function discount($articlecode, $category, $pricegroup){

$articlecode = sanitizingData($articlecode); 

$category = sanitizingData($category);

$pricegroup = sanitizingData($pricegroup);

// do priority 1

// prio 2

// prio 3

// pricelist

return $discount;

}

I would be so happy if someone could show me how to do this. I am using mysqli and php.

Many thanks

Best regards linda

Answer 1

You can do the queries with a union:

(SELECT DISCOUNT, FIXED, PERCENTAGE, 1 priority FROM PUPRIREG 
    WHERE ARTCODE = 'JO-23455' AND DISCOUNTLIST = '0013')
union
(SELECT DISCOUNT, FIXED, PERCENTAGE, 2 priority FROM PUPRIREG 
    WHERE CATEGORY = 'C15' AND DISCOUNTLIST = '0013')
union
(SELECT DISCOUNT, FIXED, PERCENTAGE, 3 priority FROM PUPRIREG 
    WHERE PRICEGROUP = 'F' AND DISCOUNTLIST = '0013')
union
(SELECT DISCOUNT, 0 fixed, 0 percentage, 4 priority FROM PUPRIREG
    WHERE PRICELIST = '01' AND PRICEGROUP = 'F')
order by priority;

The additional artificial priority column and order by ensures, that you get the discounts properly sorted.