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Posted Friday, November 16, 2012 2:58 PM
SSChasing Mays

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Hi All

I ask you guidance on this design question because this seems to be one of those things where if you don't get it right and it gets implemented much suffering will follow...

I need to design some advanced group functionality. I am calling the three functions I need 'group of groups' and 'group minus group' and 'groups plus manual'

Given the group 'Blue and Yellow'. Clearly I can add all the individual blue and yellow stars to this group but I would like to define the 'Blue and Yellow' group as being comprised of the two groups: Bluestars and Yellowstars.

Given the group '10 Brightest No Supergiants'. I would like to define this as being composed of the members of the group '10 Brightest' minus the group 'Supergiants'.

The group 'Blue stars and my current favorite star' should be composed of the group Bluestars and one other star manually selected.

Any design ideas would be much appreciated.


CREATE TABLE #Stars (Star varchar(30))
INSERT INTO #Stars (Star) VALUES ('Sirius')
INSERT INTO #Stars (Star) VALUES ('Canopus')
INSERT INTO #Stars (Star) VALUES ('Rigil Kentaurus')
INSERT INTO #Stars (Star) VALUES ('Arcturus')
INSERT INTO #Stars (Star) VALUES ('Vega')
INSERT INTO #Stars (Star) VALUES ('Capella')
INSERT INTO #Stars (Star) VALUES ('Rigel')
INSERT INTO #Stars (Star) VALUES ('Procyon')
INSERT INTO #Stars (Star) VALUES ('Achernar')
INSERT INTO #Stars (Star) VALUES ('Betelgeuse')

CREATE TABLE #StarGroups (StarGroup varchar(45))
INSERT INTO #StarGroups (StarGroup) VALUES ('10 Brightest')
INSERT INTO #StarGroups (StarGroup) VALUES ('Supergiants')
INSERT INTO #StarGroups (StarGroup) VALUES ('Bluestars')
INSERT INTO #StarGroups (StarGroup) VALUES ('Yellowstars')

INSERT INTO #StarGroups (StarGroup) VALUES ('10 Brightest No Supergiants')
INSERT INTO #StarGroups (StarGroup) VALUES ('Blue and Yellow')

INSERT INTO #StarGroups (StarGroup) VALUES ('Blue stars and my current favorite star')

CREATE TABLE #StarGroupMembers (StarGroup varchar(15),Star varchar(30))
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Sirius')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Canopus')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Rigil Kentaurus')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Arcturus')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Vega')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Capella')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Rigel')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Procyon')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Achernar')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('10 Brightest','Betelgeuse')

INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('Supergiants','Rigel')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('Supergiants','Achernar')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('Supergiants','Betelgeuse')

INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('Bluestars','Rigel')

INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('Yellowstars','Procyon')
INSERT INTO #StarGroupMembers (StarGroup,Star) VALUES ('Yellowstars','Capella')

SELECT * FROM #Stars
SELECT * FROM #StarGroups
SELECT * FROM #StarGroupMembers

DROP TABLE #Stars
DROP TABLE #StarGroups
DROP TABLE #StarGroupMembers
Post #1385868
Posted Sunday, November 18, 2012 7:24 PM


SSCrazy Eights

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A lot depends on how frequently new groups are defined, how frequently group definitions change (whether by adding new members or removing existing members or adding new subgroups or removing existing subgroups), and how deeply nested are your groups. I imagine the nesting depth will be fairly small, so it's fairly easy to design a structure in which it is easy to update group membership and to introduce new groups, and easy to provide the three functions you mention.

Since groups are potentially very large (there are a lot of red stars, for example) and since a star can be a member of many groups, it's probably a good idea to use something shorter than names to make links within the data structure (but this, of course, should be made invisible to users). That just needs a table for each star/group which uses its name and provides its identifier, perhaps as a bigint (I can't remember whether there are enough stars to need that) which can be automatically generated

You will need an additional table in addition to those in the code you posted to represent the subgroup relationship.

It is then straightforward to build total group membership from subgroups and individual members using a recursive CTE, and creating groups which are built from other groups, with or without additional individually specified elemets, becomes trivial. Subtraction is trivial too.


Tom
Post #1386127
Posted Monday, November 19, 2012 4:32 PM
SSChasing Mays

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Thank for for your response. I was using Stars as sample data, my actual data is much more mundane.

I expect my groups to contain at most 100 hundred members and the updates to be infrequent, perhaps dozens a month.

I have a new design below. I have not written a way to select group members from this structure but I expect that would be fairly easy.

Please freely critique this new structure.

You mention an additional table. What could that structure look like? Would that allow for nested subgroups?

CREATE TABLE Stars (Star varchar(30))
INSERT INTO Stars (Star) VALUES ('Sirius')
INSERT INTO Stars (Star) VALUES ('Canopus')
INSERT INTO Stars (Star) VALUES ('Rigil Kentaurus')
INSERT INTO Stars (Star) VALUES ('Arcturus')
INSERT INTO Stars (Star) VALUES ('Vega')
INSERT INTO Stars (Star) VALUES ('Capella')
INSERT INTO Stars (Star) VALUES ('Rigel')
INSERT INTO Stars (Star) VALUES ('Procyon')
INSERT INTO Stars (Star) VALUES ('Achernar')
INSERT INTO Stars (Star) VALUES ('Betelgeuse')

CREATE TABLE StarGroups (StarGroup varchar(45))
INSERT INTO StarGroups (StarGroup) VALUES ('10 Brightest')
INSERT INTO StarGroups (StarGroup) VALUES ('Supergiants')
INSERT INTO StarGroups (StarGroup) VALUES ('Bluestars')
INSERT INTO StarGroups (StarGroup) VALUES ('Yellowstars')

INSERT INTO StarGroups (StarGroup) VALUES ('10 Brightest No Supergiants')
INSERT INTO StarGroups (StarGroup) VALUES ('Blue and Yellow')

INSERT INTO StarGroups (StarGroup) VALUES ('Blue stars and my current favorite star')

CREATE TABLE StarGroupMembers (StarGroup varchar(50),Member varchar(30),MemberType varchar(30))
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Sirius','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Canopus','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Rigil Kentaurus','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Arcturus','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Vega','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Capella','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Rigel','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Procyon','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Achernar','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest','Betelgeuse','Star')

INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Supergiants','Rigel','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Supergiants','Achernar','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Supergiants','Betelgeuse','Star')

INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Bluestars','Rigel','Star')

INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Yellowstars','Procyon','Star')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Yellowstars','Capella','Star')

INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Blue and Yellow','Bluestars','GroupAdd')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Blue and Yellow','Yellowstars','GroupAdd')

INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest No Supergiants','10 Brightest','GroupAdd')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('10 Brightest No Supergiants','Supergiants','GroupSubtract')

INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Blue stars and my current favorite star','Bluestars','GroupAdd')
INSERT INTO StarGroupMembers (StarGroup,Member,MemberType) VALUES ('Blue stars and my current favorite sta','Procyon','Star')

SELECT * FROM Stars
SELECT * FROM StarGroups
SELECT * FROM StarGroupMembers

DROP TABLE Stars
DROP TABLE StarGroups
DROP TABLE StarGroupMembers
Post #1386634
Posted Tuesday, November 20, 2012 6:06 PM
SSChasing Mays

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Revised DDL/DML.

The data structure seems reasonable but I don't have an additional table that Tom suggested I may need.

My initial attempt to write a select statement to solve a group compromised of one group minus a second group has failed miserably.

I will struggle on. Comments and suggestions are certainly welcome.



--Create Groups table
CREATE TABLE [dbo].[Groups](
[GroupCode] [varchar](12) NOT NULL,
[GroupName] [varchar](40) NULL,
[GroupType] [varchar](12) NOT NULL,
[GroupDescription] [varchar](240) NULL,
CONSTRAINT [PK_Groups] PRIMARY KEY CLUSTERED
(
[GroupCode] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]


--Create GroupMembers table
CREATE TABLE [dbo].[GroupMembers](
[GroupCode] [varchar](12) NOT NULL,
[Member] [varchar](50) NOT NULL,
[MemberType] [varchar](12) NOT NULL,
CONSTRAINT [PK_GroupMembers] PRIMARY KEY CLUSTERED
(
[GroupCode] ASC,
[Member] ASC,
[MemberType] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO


ALTER TABLE [dbo].[GroupMembers] WITH CHECK ADD CONSTRAINT [FK_GroupMembers_Groups] FOREIGN KEY([GroupCode])
REFERENCES [dbo].[Groups] ([GroupCode])
GO

ALTER TABLE [dbo].[GroupMembers] CHECK CONSTRAINT [FK_GroupMembers_Groups]
GO

ALTER TABLE [dbo].[GroupMembers] WITH NOCHECK ADD CONSTRAINT [CK_GroupMembers_MemberType] CHECK (([MemberType]='GroupDelete' OR [MemberType]='GroupAdd' OR [MemberType]='Delete' OR [MemberType]='Add'))
GO

ALTER TABLE [dbo].[GroupMembers] CHECK CONSTRAINT [CK_GroupMembers_MemberType]
GO

--Create Stars table
CREATE TABLE [dbo].[Stars](
[Star] [varchar](30) NOT NULL,
CONSTRAINT [PK_Stars] PRIMARY KEY CLUSTERED
(
[Star] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

--Populate sample data into stars table
INSERT INTO Stars (Star) VALUES ('Sirius')
INSERT INTO Stars (Star) VALUES ('Canopus')
INSERT INTO Stars (Star) VALUES ('Rigil Kentaurus')
INSERT INTO Stars (Star) VALUES ('Arcturus')
INSERT INTO Stars (Star) VALUES ('Vega')
INSERT INTO Stars (Star) VALUES ('Capella')
INSERT INTO Stars (Star) VALUES ('Rigel')
INSERT INTO Stars (Star) VALUES ('Procyon')
INSERT INTO Stars (Star) VALUES ('Achernar')
INSERT INTO Stars (Star) VALUES ('Betelgeuse')

--Insert groups
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('10B','10 Brightest','Star',NULL)
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('SG','Supergiants','Star',NULL)
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('BS','Bluestars','Star',NULL)
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('YS','Yellowstars','Star',NULL)
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('10BNSG','10 Brightest No Supergiants','Star',NULL)
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('BYS','Blue and Yellow','Star',NULL)
INSERT INTO Groups (GroupCode,Groupname,GroupType,GroupDescription) VALUES ('BSFAVE','Blue stars and my favorite star','Star',NULL)
--Insert groups members


INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Sirius','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Canopus','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Rigil Kentaurus','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Arcturus','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Vega','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Capella','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Rigel','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Procyon','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Achernar','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10B','Betelgeuse','Add')

INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('SG','Rigel','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('SG','Achernar','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('SG','Betelgeuse','Add')

INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('BS','Rigel','Add')

INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('YS','Procyon','Add')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('YS','Capella','Add')

INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10BNSG','10B','GroupAdd')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('10BNSG','Supergiants','GroupDelete')

INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('BYS','BS','GroupAdd')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('BYS','YS','GroupDelete')

INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('BSFAVE','BS','GroupAdd')
INSERT INTO GroupMembers (GroupCode,Member,MemberType) VALUES ('BSFAVE','Procyon','Add')


DECLARE @GroupCode [varchar](12)
--SET @GroupCode= 'BSFAVE'
--SET @GroupCode= '10B'
SET @GroupCode= '10BNSG'
--SET @GroupCode= 'BS'
--SET @GroupCode= 'BYS'
--SET @GroupCode= 'SG'
--SET @GroupCode= 'YS'



SELECT
@GroupCode,
GroupCode,
Member
FROM GroupMembers
WHERE
GroupCode IN
(
SELECT
Member
FROM GroupMembers GM
WHERE
GM.GroupCode = @GroupCode AND
MemberType = 'GroupAdd'
)
/*
AND GroupCode NOT IN
(
SELECT

GroupCode

FROM GroupMembers
WHERE
GroupCode IN
(
SELECT
Member
FROM GroupMembers GM
WHERE
GM.GroupCode = '10BNSG' AND
MemberType = 'GroupAdd'
)
)
*/
--SELECT * FROM Stars
--SELECT * FROM Groups
SELECT * FROM GroupMembers WHERE GroupCode = @GroupCode



DROP TABLE GroupMembers
DROP TABLE Groups
DROP TABLE Stars
Post #1387200
Posted Wednesday, November 21, 2012 9:17 AM


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Your design is fundamentally wrong. A star is an entity, which has attributes like color, etc. Why is the identifier, the name of the star (which should have been “star_name”, not just “star”) is a complete entity in itself? No other atributes! Groupings are a relationship (NOT an entity) among the stars. This design error is called “attribute splitting” and you have huge one. You spread the attributes of a star over multiple tables using a hand grenade! Then you try splice a properly design set back from parts with PK-FK.

Your encoding schemes are sloppy, too. We like fixed length codes. Why so many NULL-able columns? Why so many vague data element names? Think about your groups; you have to design data and you have failed to do that.

Look at :
('SG', 'Supergiants') This is a valid encoding using a nominal scale. It shows no research, but it has the right semantics for an auxillary table.

But you put queries in the same encoding, behold:
('10B', '10 Brightest')
and
('10BNSG', '10 Brightest, No Supergiants')

As the list changes, you will be re-computing these hidden queries over and over and over and over. Yuck!

Let me give you another quote, from the Essay "The Analytical Language of John Wilkins" by Jorge Luis Borges to give you a feel for how awful this design is:

"These ambiguities, redundancies, and deficiencies recall those attributed by Dr. Franz Kuhn to a certain Chinese encyclopedia entitled Celestial Emporium of Benevolent Knowledge. On those remote pages it is written that animals are divided into (a) those that belong to the Emperor, (b) embalmed ones, (c) those that are trained, (d) suckling pigs, (e) mermaids, (f) fabulous ones, (g) stray dogs, (h) those that are included in this classification, (i) those that tremble as if they were mad, (j) innumerable ones, (k) those drawn with a very fine camel's hair brush, (l) others, (m) those that have just broken a flower vase, (n) those that resemble flies from a distance."

A quick look at Wikipedia would have got your the industry standard encoding for stars. It is called the Morgan_Keenan system and it has a nice regular expression. Most stars are currently classified using the letters O, B, A, F, G, K, and M, where O stars are the hottest and the letter sequence indicates successively cooler stars up to the coolest M class. According to informal tradition, O stars are called "blue", B "blue-white", A stars "white", F stars "yellow-white", G stars "yellow", K stars "orange", and M stars "red", even though the actual star colors perceived by an observer may deviate from these colors depending on visual conditions and individual stars observed. This letter is followed by a number from 0 to 9 indicating tenths of the range between two star classes and the is the luminosity class expressed by Roman numerals I, II, III, IV and V.
For example, the Sun has the spectral type G2V, which might be interpreted as "a 'yellow' two tenths towards 'orange' main-sequence star". The apparently brightest star, Sirius, has type A1V.

CREATE TABLE Stars
(star_name VARCHAR(30) NOT NULL PRIMARY KEY,
mk_code CHAR(6) NOT NULL
REFERENCES Morgan_Keenan (mk_code)
ON UPDATE CASCADE,

CREATE TABLE Morgan_Keenan
(mk_code CHAR(6) NOT NULL PRIMARY KEY
CHECK (mk_code LIKE '[OBAFGKM][0-9]I'
OR mk_code LIKE '[OBAFGKM][0-9]II'
OR mk_code LIKE '[OBAFGKM][0-9]III'
OR mk_code LIKE '[OBAFGKM][0-9]IV'
OR mk_code LIKE '[OBAFGKM][0-9]V'),
mk_description VARCHAR(100) NOT NULL);

INSERT INTO Stars
VALUES ('Sirius', 'A1V'),
('Sol', 'G2V'),
etc;

Now you can use a regular expression to get subsets. For example:

CREATE VIEW Red_Stars (star_name)
AS
SELECT star_name FROM Stars WHERE mk_code LIKE 'M%';

The top ten is a little harder, but not hard:

WITH Star_Luminosity
AS
(SELECT star_name, mk_code,
(CASE SUBSTRING (mk_code, 3, 5)
WHEN 'I' THEN 1
WHEN 'II' THEN 2
WHEN 'III' THEN 3
WHEN 'IV' THEN 4
WHEN 'V' THEN 5 END AS luminosity
FROM Stars),
Star_Lumen_Rank (star_name, luminosity, lumen_rank)
AS
(SELECT star_name, luminosity,
DENSE_RANK() OVER (ORDER BY luminosity DESC)
FROM Star_Luminosity)
SELECT *
FROM Star_Lumen_Rank
WHERE lumen_rank <= @in_rank)

The rest of the schema seems be another design flaw. You have actions in the database! NO! NO! It is called a “data base” for a reason; it has only data. This is the foundations of all tiered architecture; data and processes are separated.



Books in Celko Series for Morgan-Kaufmann Publishing
Analytics and OLAP in SQL
Data and Databases: Concepts in Practice
Data, Measurements and Standards in SQL
SQL for Smarties
SQL Programming Style
SQL Puzzles and Answers
Thinking in Sets
Trees and Hierarchies in SQL
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