Conditional Grouping - sql-server

Question

I have item and buyer tables. Both tables have their individual category tables i.e. itemCategory and buyerCategory
CREATE TABLE #itemCategory
(
itemCategoryCode char(4) NOT NULL PRIMARY KEY
, itemCategoryName char(20) NOT NULL
);
INSERT INTO #itemCategory
VALUES ('I001', 'Item Category A')
,('I002', 'Item Category B')
,('I003', 'Item Category C');
CREATE TABLE #buyerCategory
(
buyerCategoryCode char(4) NOT NULL PRIMARY KEY
, buyerCategoryName char(20) NOT NULL
);
INSERT INTO #buyerCategory
VALUES ('B001', 'Buyer Category A')
,('B002', 'Buyer Category B')
,('B003', 'Buyer Category C');
CREATE TABLE #item
(
itemCode char(5) NOT NULL PRIMARY KEY
, itemName char(30) NOT NULL
, itemCategoryCode char(4) NOT NULL FOREIGN KEY REFERENCES itemCategory(itemCategoryCode)
);
INSERT INTO #item
VALUES ('IT001', 'Item A', 'I001')
, ('IT002', 'Item AA', 'I001')
, ('IT003', 'Item AAA', 'I001')
, ('IT004', 'Item B', 'I002')
, ('IT005', 'Item BB', 'I002')
, ('IT006', 'Item BBB', 'I002')
, ('IT007', 'Item C', 'I003')
, ('IT008', 'Item CC', 'I003')
, ('IT009', 'Item CCC', 'I003');
CREATE TABLE #buyer
(
buyerCode char(5) NOT NULL PRIMARY KEY
, buyerName char(30) NOT NULL
, buyerCategoryCode char(4) NOT NULL FOREIGN KEY REFERENCES buyerCategory(buyerCategoryCode)
);
INSERT INTO #buyer
VALUES ('BY001', 'Buyer A', 'B001')
, ('BY002', 'Buyer AA', 'B001')
, ('BY003', 'Buyer AAA', 'B001')
, ('BY004', 'Buyer B', 'B002')
, ('BY005', 'Buyer BB', 'B002')
, ('BY006', 'Buyer BBB', 'B002')
, ('BY007', 'Buyer C', 'B003')
, ('BY008', 'Buyer CC', 'B003')
, ('BY009', 'Buyer CCC', 'B003');
I have a table itemRate table which define rate of item for individual buyer which also has isActive column.
CREATE TABLE #itemRate
(
itemCode char(5) NOT NULL FOREIGN KEY REFERENCES item(itemCode)
, buyerCode char(5) NOT NULL FOREIGN KEY REFERENCES buyer(buyerCode)
, [rate] int NULL
, isActive NOT NULL BIT
);
INSERT INTO #itemRate
VALUES ('IT001', 'BY001', 3.5, '1')
, ('IT002', 'BY001', 4.5, '1')
, ('IT003', 'BY001', 5.5, '0')
, ('IT004', 'BY004', 1.5, '0')
, ('IT005', 'BY004', 2.5, '1')
, ('IT006', 'BY004', 7.5, '0')
, ('IT006', 'BY005', 5.5, '1')
, ('IT005', 'BY005', 2.5, '0')
, ('IT001', 'BY007', 2.5, '0')
, ('IT002', 'BY008', 4.5, '0')
, ('IT003', 'BY007', 6.5, '0');
I am looking for a SQL query where I can get result of following columns itemCategoryCode, buyerCategoryCode, [rate]
There can be multiple scenarios on itemRate table and in all cases query will collect MAX([rate]) column while grouping for itemCategoryCode and buyerCategoryCode
Only exception is when there is multiple items (under same itemCategory) has rates value to the same buyer (not same buyerCategory) and there are no other buyer of the same buyerCategory then system will get the MAX[rate] value of only isActive=1 records.
In the sample data of itemRate table, the result of the query should be
itemCategoryCode
buyerCategoryCode
rate
I001
B001
4.5
I002
B002
7.5
I001
B003
6.5
Let me explain further. a) It is not mandatory that all buyers under the same buyerCategory has any rates defined in itemRates table.
b) In the sample data, where IT003 is bought by BY001 for rate of 5.5 but because there are no other buyer (of same buyerCategory) who have bought any items of itemCategory I001, and since isActive of that record (IT003, BY001, 5.5, 0) is false, the query will not consider it in MAX.
Now compare this with sample data ('IT001', 'BY007', 2.5, '0'), ('IT002', 'BY008', 4.5, '0') and ('IT003', 'BY007', 6.5, '0'); although all this record have false value in isActive but since there are two buyers of same buyerCategory i.e. BY007 and BY008... the query will not consider isActive value hence result of MAX([rate]) would be 6.5.
I hope I clarified my requirements clearly... please let me know, if you need any further clarifications.
Thanks in advance

Answer 1

Thanks for the additional detail on the requirements. I believe this gets you what you want:
CREATE TABLE #itemCategory
(
itemCategoryCode char(4) NOT NULL PRIMARY KEY
, itemCategoryName char(20) NOT NULL
);
INSERT INTO #itemCategory
VALUES ('I001', 'Item Category A')
,('I002', 'Item Category B')
,('I003', 'Item Category C');
CREATE TABLE #buyerCategory
(
buyerCategoryCode char(4) NOT NULL PRIMARY KEY
, buyerCategoryName char(20) NOT NULL
);
INSERT INTO #buyerCategory
VALUES ('B001', 'Buyer Category A')
,('B002', 'Buyer Category B')
,('B003', 'Buyer Category C');
CREATE TABLE #item
(
itemCode char(5) NOT NULL PRIMARY KEY
, itemName char(30) NOT NULL
, itemCategoryCode char(4) NOT NULL FOREIGN KEY REFERENCES itemCategory(itemCategoryCode)
);
INSERT INTO #item
VALUES ('IT001', 'Item A', 'I001')
, ('IT002', 'Item AA', 'I001')
, ('IT003', 'Item AAA', 'I001')
, ('IT004', 'Item B', 'I002')
, ('IT005', 'Item BB', 'I002')
, ('IT006', 'Item BBB', 'I002')
, ('IT007', 'Item C', 'I003')
, ('IT008', 'Item CC', 'I003')
, ('IT009', 'Item CCC', 'I003');
CREATE TABLE #buyer
(
buyerCode char(5) NOT NULL PRIMARY KEY
, buyerName char(30) NOT NULL
, buyerCategoryCode char(4) NOT NULL FOREIGN KEY REFERENCES buyerCategory(buyerCategoryCode)
);
INSERT INTO #buyer
VALUES ('BY001', 'Buyer A', 'B001')
, ('BY002', 'Buyer AA', 'B001')
, ('BY003', 'Buyer AAA', 'B001')
, ('BY004', 'Buyer B', 'B002')
, ('BY005', 'Buyer BB', 'B002')
, ('BY006', 'Buyer BBB', 'B002')
, ('BY007', 'Buyer C', 'B003')
, ('BY008', 'Buyer CC', 'B003')
, ('BY009', 'Buyer CCC', 'B003');
CREATE TABLE #itemRate
(
itemCode char(5) NOT NULL FOREIGN KEY REFERENCES item(itemCode)
, buyerCode char(5) NOT NULL FOREIGN KEY REFERENCES buyer(buyerCode)
, [rate] decimal(2,1) NULL
, isActive bit not NULL
);
INSERT INTO #itemRate
VALUES ('IT001', 'BY001', 3.5, '1')
, ('IT002', 'BY001', 4.5, '1')
, ('IT003', 'BY001', 5.5, '0')
, ('IT004', 'BY004', 1.5, '0')
, ('IT005', 'BY004', 2.5, '1')
, ('IT006', 'BY004', 7.5, '0')
, ('IT006', 'BY005', 5.5, '1')
, ('IT005', 'BY005', 2.5, '0')
, ('IT001', 'BY007', 2.5, '0')
, ('IT002', 'BY008', 4.5, '0')
, ('IT003', 'BY007', 6.5, '0');
with #ratesAndCategories as
(
select ir.*, bu.buyerCategoryCode, it.itemCategoryCode
from #itemRate ir
join #buyer bu on bu.buyerCode = ir.buyerCode
join #item it on it.itemCode = ir.itemCode
)
select rc.itemCategoryCode,
rc.buyerCategoryCode,
--max(iif(otherBuyers.c = 0 and rc.isActive = 0, null, rc.rate))
max(case when otherBuyers.c = 0 and rc.isActive = 0 then null else rc.rate end)
from #ratesAndCategories rc
cross apply (
select count(*)
from #ratesAndCategories
where buyerCode != rc.buyerCode
and buyerCategoryCode = rc.buyerCategoryCode
and itemCategoryCode = rc.itemCategoryCode
) otherBuyers(c)
group by rc.itemCategoryCode,
rc.buyerCategoryCode;