combining multiple queries / query optimization - sql-server

Question

I have made a little example data that I modify in three steps. I cant do it in one, maybe there is a clever way with some logic? I use Microsoft SQL Server
This code will generate the four base tables with example data and the step by step queries I want to combine, the result at the end should have 8 entries:
Reference table:
CREATE TABLE ref
(
ID int NOT NULL
NR int NOT NULL
CONSTRAINT KEYS PRIMARY KEY (ID, NR)
);
INSERT INTO ref
VALUES (1234, 223), (1234, 224), (1234, 225),
(1235, 123), (1235, 124), (1236, 540),
(1236, 541), (1237, 233), (1237, 234);
Con1 table:
CREATE TABLE con1
(
NR int NOT NULL
flag int NOT NULL
PRIMARY KEY (NR)
);
INSERT INTO con1
VALUES (123, 0), (124, 1), (125, 0),
(220, 0), (222, 0), (223, 0),
(224, 0), (225, 1), (300, 0),
(540, 1), (541, 1);
Con2 table:
CREATE TABLE con2
(
NR int NOT NULL
ID int NOT NULL
PRIMARY KEY (NR)
);
INSERT INTO con2
VALUES (123, 1235), (124, 1235), (125, 1243),
(220, 1296), (222, 1255), (223, 1234),
(224, 1234), (225, 1234), (300, 1267),
(540, 1236);
Info table:
CREATE TABLE info
(
NR int NOT NULL
SNR int NOT NULL
SSNR int NOT NULL
Level int not NULL
CONSTRAINT KEYS PRIMARY KEY (NR, SNR, SSNR)
);
INSERT INTO info
VALUES (123, 1, 1, 1), (123, 1, 2, 2),
(123, 1, 3, 2), (123, 2, 1, 1),
(123, 2, 2, 2), (123, 2, 3, 2),
(124, 1, 1, 1), (124, 1, 2, 2),
(124, 1, 3, 2), (125, 1, 1, 1),
(125, 1, 2, 2), (125, 1, 3, 2),
(125, 1, 4, 3), (125, 1, 5, 3),
(220, 1, 1, 1), (220, 1, 2, 2),
(223, 1, 1, 1), (223, 1, 2, 2),
(224, 1, 1, 1), (224, 1, 2, 2),
(224, 1, 3, 2), (225, 1, 1, 1),
(225, 1, 2, 2), (300, 1, 1, 1),
(300, 1, 2, 2), (300, 2, 1, 1),
(300, 2, 2, 2), (540, 1, 1, 1),
(541, 1, 1, 1);
Step #1:
SELECT *
FROM con1
INNER JOIN con2 ON con1.NR = con2.NR
WHERE con1.flag = 1
Step #2:
SELECT ref.*
FROM ref
INNER JOIN step1 ON ref.ID = step1.ID
Step #3:
SELECT *
FROM step2
INNER JOIN info ON step2.NR = info.NR
WHERE info.Level = 1
I tried some different ways but always get too much resulting rows
the result should look like this:
ID
NR
Level
SNR
SSNR
1234
223
1
1
1
1234
224
1
1
1
1234
225
1
1
1
1235
123
1
1
1
1235
123
1
2
1
1235
124
1
1
1
1236
540
1
1
1
1236
541
1
1
1
It should be all entries from info with Level=1
excluding:
all NR that do not occur in the intersection of con1 and con2
all NR that con1 lists with flag = 0
but including:
all excluded NR that run with the same ID (according to ref) as any NR not excluded prior
the result has the same columns as info with on NR matching IDs from ref

Answer 1

You can do this easily with Common Table Expressions:
with step1 As (
Select *
From con1
Inner Join con2 On con1.NR = con2.NR
Where con1.flag = 1
), step2 As (
Select ref.*
From ref
Inner Join step1 On ref.ID = step1.ID
)
Select *
From step2
Inner Join info On step2.NR = info.NR
Where info.Level = 1