Stairway to Data, Level 2: Numerics
A confusion about the nature of numbers can lead to a number of problems in database applications. Joe Celko gives a simple guide to the subject
A confusion about the nature of numbers can lead to a number of problems in database applications. Joe Celko gives a simple guide to the subject
Character-handling in SQL is not particularly straightforward, and confusion about collation and character encoding is a common cause of problems with searching, joining, and sorting.
Joe Celko discusses Nominal, Categorical, Absolute, Ordinal and Rank scales. These are the weakest scales we can use, starting with the weakest.
Joe Celko introduces more powerful scales such as Interval, Log interval and ratio scales; before moving on to conversions, punctuation and units. Finally he gives guidelines as to how best to use scales in a database.
Joe discusses how to deal with the kinds of encoding schemes, how to use them and how to design them. He discusses Enumeration, Measurement, Abbreviation and Algorithmic categories
Joe discusses Hierarchical, Vector and Concatenation encoding before rounding up with general guidelines for designing encoding schemes.
Before you start to think about your database schema or tables, you need to consider your data: the type of data it is, the scale you use for values. It needs to be unique, precise and unambiguous. Then you need to name it in such a way that it can be generally understood. Joe Celko explains...
A clear understanding of SQL Data Types and domains is a fundamental requirement for the Database Developer, but it is not elementary. If you select the most appropriate data type, it can sidestep a variety of errors. Furthermore, if you then define the data domains as exactly as possible via constraints, you can catch a variety of those problems that would otherwise bedevil the work of the application programmer.
There are several types of tables, each with their special requirements for rules and integrity constraints. Whatever the requirement, table-level constraints will ensure that the rules are enforced and data integrity is maintained.
Having described tables, Joe Celko explains how to make them work together as a database and touches on what Entity Relationships and Views are.
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Ruko Soho Emas, Jl. Klampis Jaya No.39, Klampis Ngasem, Sukolilo, Surabaya, Jawa Timur 60117
I have this data in a table called dbo.NFLTeams
TeamID TeamName City YearEstablished ------ -------- ---- --------------- 1 Cowboys Dallas 1960 2 Eagles Philadelphia 1933 3 Packers Green Bay 1919 4 Chiefs Kansas City 1960 5 49ers San Francisco 1946 6 Broncos Denver 1960 7 Seahawks Seattle 1976 8 Patriots New England 1960If I run this code, how many rows are returned?
SELECT TOP 2
json_objectagg('Team' : TeamName)
FROM dbo.NFLTeams;
See possible answers