Data Modeling and Management · Topic 2 of 3
Field Data Type Considerations
Salesforce field types for app builders: choosing text, number, picklist, formula and lookup fields, external IDs, and what changing a field type does.
- 4 min
- Text holds up to 255 characters; long and rich text areas hold more.
- Restricted picklists block values not in the list, even through the API.
- External ID fields support upsert and integration matching.
What it is
Every custom field has a data type, such as Text, Number, Date, Picklist or Lookup. The type decides what the field can store, how it is validated, how it appears on pages and in reports, and what formulas and automation can do with it.
Choosing the right type at the start avoids data loss later, because changing a type can delete or truncate existing values.
How it works
Common data types
| Type | Use it for |
|---|---|
| Text | Short free text, up to 255 characters |
| Text Area (Long) and Rich Text | Long descriptions and notes |
| Number, Currency, Percent | Values used in calculations, with set decimal places |
| Date, Date/Time, Time | Points in time |
| Checkbox | True or false |
| Picklist | One value from a defined list |
| Picklist (Multi-Select) | Several values from a list |
| Email, Phone, URL | Formatted contact values that users can click |
| Auto Number | A system-generated sequence, such as INV-0001 |
| Formula | A read-only value calculated from other fields |
| Roll-Up Summary | A COUNT, SUM, MIN or MAX of detail records |
| Lookup and Master-Detail | Relationships to other records |
| Geolocation | Latitude and longitude |
Picklists
- A restricted picklist accepts only its defined values, including through the API.
- A global value set shares one list of values across several picklist fields.
- Dependent picklists filter one picklist's values by a controlling field.
- Record types can show a different subset of picklist values to different users.
Multi-select picklists are harder to use in reports, formulas and filters. Prefer a single-select picklist, or a related object, when you need clean reporting.
Field attributes
| Attribute | Effect |
|---|---|
| Required | Must have a value on every save, from any source |
| Unique | No two records can share the same value |
| External ID | Indexed and used to match records during imports and integrations |
| Default value | Filled in when a record is created |
External ID fields help when data comes from another system: imports can upsert records by matching on the external ID instead of the Salesforce record ID.
Changing a field's data type
Changing a type is possible for many fields, but with consequences:
- Values that do not fit the new type can be lost, such as text that is not a number.
- Some changes are blocked, for example when the field is used in a formula, roll-up summary or other dependency.
- Some conversions are not offered at all, such as turning a formula field into a regular field; you create a new field instead.
Always back up data before changing a type on a field that holds data.
Deleting fields
A deleted custom field goes to the Deleted Fields list, where it can be restored for a limited time with its data. A field cannot be deleted while it is referenced elsewhere, such as in a formula, flow or Apex.
A worked example: a team stores contract length as free text, such as "12 months" and "1 year". Reporting on it is impossible. The builder creates a new Number field, fills it from the old values with a data load after cleaning them, updates the layouts and reports, and then deletes the old text field rather than converting it and losing the values that do not convert.
Choose a picklist rather than free text whenever values must be reported on or used in automation.
How the exam asks about this
- "Integration must match records from another system." An External ID field.
- "The same list of values on several objects." A global value set.
- "Show only some values to one team." A record type with its own picklist values.
What to remember for the exam
- Text holds up to 255 characters; long and rich text areas hold more.
- Restricted picklists block values not in the list, even through the API.
- External ID fields support upsert and integration matching.
- Changing a data type can lose data; some changes are blocked by dependencies.
- Prefer single-select picklists over multi-select for reporting.
Changing a field from Text to Number deletes values that are not valid numbers. Check the data first.
Common mistakes
Using free text for values the business reports on. Use a picklist.
Assuming a required field only applies on the page layout. A field set as required at field level applies to every save.
Converting a field type without a backup. Values that cannot convert are lost.
Check yourself
Which field attribute lets an import match records using another system's identifier?
The External ID attribute.
What does a restricted picklist prevent?
Saving any value that is not in the picklist's defined list, including through the API.
What risk comes with changing a field's data type?
Values that do not fit the new type can be lost.
Topic 2 of 3 in Data Modeling and Management
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