2. ASCII
ASCII is an acronym for American Standard Code for Information Interchange. The ASCII set consists of 7-bit codes that represent 128 standard characters, including letters, numbers, and symbols. The first 128 characters in the ASCII set, the extended ASCII set, and the ANSI set are the same.
5. Concatenation of VARCHAR fields yields NULL
When you have a concatenation of two or more CHAR or VARCHAR fields in a SELECT statement, and one of the fields is NULL, the resulting value will be NULL.
by Jeffrey K. Tyzzer. In 1970, Dr. E.F. Codd's seminal paper "A Relational Model for Large Shared Databanks" was published in Communications of the ACM. This paper introduced the topic of data normalization, so-named because, at the time, President Nixon was normalizing relations with China.
Data normalization is a technique used during logical data modeling to ensure that there is only one way to know a fact, by removing all structures that provide more than one way to know the same fact as represented in a database relation (table). The goal of normalization is to control and eliminate redundancy, and mitigate the effects of modification anomalies -- which are generally insertion and deletion anomalies. (Insertion anomalies occur when the storage of information about one attribute requires additional information about a second attribute. Deletion anomalies occur when the deletion of one fact results in the loss of a second fact).
Normalization There are six generally recognized normal forms of a relation: first normal form, second normal form, third normal form, Boyce/Codd normal form, fourth normal form, and fifth normal form, also called projection/join normal form. Other normal forms (e.g., Domain/Key) exist but will not be discussed here. The normal forms are hierarchical, i.e., each normal form builds upon its predecessor. Although many people consider a relation to be normalized only when it is in third normal form, technically speaking, a relation in only first normal form can be considered...
15. ElevateDb - The New Kid on the DB Block
For years, Elevate Software has provided the elegant, fast, and stable DBISAM database. They're recently released ElevateDB, an amazing follow-up.
17. Learn the Three Normal Forms in One Sentence
The three normal forms can be summed up in the following phrase: All the fields of a table should relate to the key, the whole key, and nothing but the key.
18. Master Table
A master table in a multitable relationship is the primary table. For every record in the master table, there can be many records in the detail table. If you are only dealing with one table, then it is the master table. A detail table in a multitable relationship is the table whose records are subordinate to those of the master table. A detail table is also called a slave table, a child table, or a many table.
19. Naming Fields: Choose a Context Name
When naming fields/columns in a table, use ONE name for the data in the field. For example, although states are called provinces and other names in other coutries, use one or the other in the database but not both. Use CompanyState, avoid CompanyStateProvince. Use labels in your website or program to switch context.
21. ODBMS or RDBS?
For several years now, Object Relational databases have intrigued many developers, myself included. Most of us also rely on more traditional RDBMS systems. Well, a debate is raging, and you're invited to join.
22. Optimistic Locking
A locking mechanism that allows other users to edit a record that is currently being edited. Essentially, last in wins or edits are discarded usually with an error.
25. oracle silent mode installation using response file
You can automate the installation and configuration of Oracle software, either fully or partially, by specifying a response file when you start the Oracle Universal Installer.
31. Standard Delimited Format (SDF)
SDF is an acronym for standard delimited format. An SDF is a text file formatted in a particular style. Each field is enclosed in quotation marks and separated by a comma. Each line ends with a carriage return and a linefeed.
32. Tab-delimited format (TDF)
In a Tab-delimited format (TDF) file, each field is delimited by a tab character. Each record is delimited with a carriage return and line feed. TDF has the advantages of being immune to commas and quotation marks within the data itself.
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