Pattern matching and arithmetical operators

Pattern matching using LIKE

The LIKE condition allows you to use wildcards in the WHERE clause of an SQL statement. This allows pattern matching.
The patterns that you can choose from are:

• "%" allows you to match any string of any length (including zero length)
• "_" allows you to match on a single character

NOT LIKE examines whether the given section is not present in the string.

Arithmetical operators

The arithmetical standard operators for addition (+), subtraction (-), multiplication (*) and division (/) can all be used for numerical constant or for attributes with a numerical domain. This allows attributes in a request to be calculated together.

In the above example the result is a relation with three attributes. The third attribute is named "Usury" since "Price/Size" is not a good name and stands for the price per unit. We define that if it lies over 15, it is overpriced ("Usury").

Arithmetical operators can be used in the SELECT part of a request or in the conditions.

In the SELECT or FROM part of a request, attributes and relations can be given a different name by the command AS: <Attribute/Relation> AS <new name> (The key word AS can be omitted). This can be used to give a calculated value a meaningful name (see example), or to make SQL requests easier to read.