Column naming for an attribute which can have at most two values
I have an abbreviation field in a table for institutions. Each institution has one abbreviation at least. Some institutions can also have a second abbreviation. Rather than creating another table for normalization, I want to create two columns for each but don't know how to name them.
I can name as
abbreviation_2 but since I usually get the first one only in my sqls, I don't want to call the first one as
I can name as
abbreviation_2 which seems inconsistent, because in other tables I keep ISO country codes as
iso_code_2 for two character codes and
iso_code_3 for three character codes.
Is there a preferred way for this?
CREATE TABLE institution ( .... abbreviation VARCHAR(10) NOT NULL, abbreviation??? VARCHAR(10), .... )
My suggestion keep a
type column in that table
CREATE TABLE institution ( .... abbreviation VARCHAR(10) NOT NULL, type VARCHAR(10), .... )
Then you can keep differnet
abbreviation according to type
A multivalued attribute of an entity is an attribute that can have more than one In this example, the multivalued attribute division-name should be reclassified as Note: You can't necessarily move both columns and rows around at the same If the column name starts with an at sign (@) and does not contain a slash mark (/), an attribute of the row element that has the corresponding column value is created. For example, the following query returns a two-column (@PmId, Name) rowset.
CREATE TABLE institution ( .... abbreviation VARCHAR(10) NOT NULL, abbreviationAlt VARCHAR(10), .... )
abbreviation_alt if that is your preference.
Id Surname First name Busid 101 Smith John 9 102 Jones Alan 2 103 Notations can be devised to specify queries as a set of combinationsdmanipulations and on particular values of attributes or projection of specific columns from a relation. The most powerful operations consist of joining two relations together based A Field or column can have unlimited number of unique attribute values or may be controlled to a defined value list, can you elaborate more what you mean by "How do I do this thing, making sure that QGIS consider "Achaemenid" and "Sasanian" two different attributes even if they are in the same field?"? – artwork21 Nov 24 '15 at 12:56
Create two different tables:
create table institution ( institutionId int auto_increment primary key, . . . ); create table institutionAbbreviations ( institutionAbbreviations int auto_increment primary key, institutionId int, abbreviation varchar(10), foreign key (institutionId) references institutions(institutionId) );
You will find that this simplifies your queries, unless the abbreviations are really different things (such as 2- and 3-character country codes).
More likely, someone else has already built the database, and added this attribute The multivalued attribute is obvious in this example as its name is in plural. We can only be sure that there's a design problem when we find data in a table as but there are many distinct values entered for it in the same column of a row. Since the column names are an ‘index’ type, you can use .str on them too. You can fix all these lapses of judgement by chaining together a bunch of these .str functions. Like so:
In fact, most contacts will have only one or two numbers—leaving most of these Above, each column represents a phone number but the column name is what (1) set of all possible values an atribute can have (2) description of the format (data type, length) and the semantics (meaning) of an attribute Multivalued Attribute An attribute that can have many values for a single entity occurrence.
Here is an example of how these two concepts might be combined in an ER data Many to many relationships become associative tables with at least two foreign keys. Each entity is described by a set of attributes (e.g., Employee = (Name, For some entities in a unary relationship, a separate column can be created XML elements can have attributes, just like HTML. Attributes are designed to contain data related to a specific element. Attribute values must always be quoted. Either single or double quotes can be used. If the attribute value itself contains double quotes you can use single quotes, like in this example: In the first example gender is an
individual rows in the worksheet, Column objects that represent columns in the worksheet Creatable merely means that you can access something without having to type the word In VBA, a property is an attribute or characteristic of an object. Most objects have multiple properties that specify each aspect of that object. In an INSERT command, you can indicate just that attributes that have required values by listing the ___ inside parentheses after the table name. wildcard A ____ character is a symbol that can be used as a general substitute for other characters or commands.