Everything about Column Database totally explained
In the context of a
relational database table, a
column is a set of
data values of a particular simple
type, one for each
row of the table. The columns provide the structure according to which the rows are composed.
The term
field is often used interchangeably with
column, although many consider it more correct to use
field (or
field value) to refer specifically to the single item that exists at the intersection between one row and one column.
For example, a table that represents companies might have the following columns:
- ID (integer identifier, unique to each row)
- Name (text)
- Address line 1 (text)
- Address line 2 (text)
- City (integer identifier, drawn from a separate table of cities, from which any state or country information would be drawn)
- Postal code (text)
- Industry (integer identifier, drawn from a separate table of industries)
- etc.
Each row would provide a data value for each column and would then be understood as a single structured data value, in this case representing a company. More formally, each row can be interpreted as a
relvar, composed of a set of
tuples, with each tuple consisting of the two items: the name of the relevant column and the value this row provides for that column.
| Row 1 Column 1 | Row 1 Column 2
|
| Row 2 Column 1 | Row 2 Column 2
|
| Row 3 Column 1 | Row 3 Column 2
|
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