Fields and data types

Fields define the data that can be stored in a record. Fields define the name that is used to retrieve data from a record and the data type the data will be stored as. Compared to a spreadsheet tabel, fields are the name and data type of columns.

Adding and editing fields

In the "fields" tab in each class page in the blueprint we can add and remove the fields that belong to it. More properties can be set at the field details.

Data types

The data type of a field defines what type of input field is used for the data. Every data type has it's own constraints, for example when the data type is "date", only valid dates will be allowed as input. Use the "Select from a list with explanations"-button to select the desired data type. If you do not specify a data type, "text" will be used as default. 

The most common data types are:

• autonumber
per object (record) in the class a new sequence number will be generated. This data type is used for key fields.
• text
normal text on a single line.
• whole number
whole numbers (integers), positive and negative.
• decimal number
decimal numbers, positive and negative.
• boolean
can have 2 values: true or false. Used for yes/no or on/off properties.
• date
a date.
• time
a time.
• date & time
the combination of a date and time.
• email address
the values will be checked to make sure they are valid email addresses.
• memo
a text field to store multi line text.
• money
to store monetary values.

Some examples: for fields like "first name" and "last name", the data type "text" will do. For a field "product number" or "id number" the data type could be set to "whole number". However, if "id number" is used as a key field the values should be unique, meaning that identical numbers are not allowed. Users could check and enter the unique values manually, but in most cases it is preferable to let the Application Engine handle this task. To activate this, set the data type of your key field to "Autonumber".

You can change the data type after it has been used to enter records, but this can have consequences for the data in the active database.  E.g. when you change the data type from ‘text’ to ‘whole number’ all data containing non-numerical characters will be lost.  

In addition to the fixed data types, there are two other options:

• global lookup lists
  When you have defined global lookup lists (see Using lookup lists) you can also select one of these lookup lists.
   
• foreign classes
  When you have defined relations (see Relations between classes) then you can also select an other class as foreign class. 

When the field is a foreign key field, a lookup list will be created dynamically from the records in the foreign class. The keys in the lookup list items are created from the key of the foreign records. The labels in the lookup list items are created from the labels of the foreign records.

Please read the other tutorials to learn more about these options.

Read more about field properties concerning security here.