{"slug": "seven-types-of-data-extensions-we-use-on-sfmc-projects", "title": "Seven Types of Data Extensions We Use on SFMC Projects", "summary": "The article summarizes seven types of Data Extensions (DEs) in Salesforce Marketing Cloud (SFMC), including Sendable DEs for email campaigns, Lookup DEs for reference data, Filtered DEs for point-and-click segmentation (which require manual refreshing), Random Split DEs for A/B testing, Shared DEs for cross-Business Unit access, Send Log DEs for tracking email sends, and DEs with Retention Policies for auto-purging old data. It emphasizes that understanding these distinctions—such as not using a Lookup DE for sending or forgetting to refresh a Filtered DE—prevents costly architecture mistakes. The article concludes that most projects use a mix of these types, and correctly identifying the DE type before creation saves significant time versus fixing errors later.", "body_md": "\"Data Extension\" is the generic term, but SFMC supports several DE types with different behaviors. Knowing the distinctions saves you from trying to send email from a lookup DE or forgetting to refresh a Filtered DE before a campaign.\nHere's the reference we hand to every new engineer.\nThe main type used for sending email. Requirements:\nThis is the DE you pick when you send a campaign or set up a Journey with Data Extension entry source. No send can happen without one.\nReference data that AMPscript Lookup() pulls into email templates at render time. Common examples:\nNot sendable, no EmailAddress field needed. Used by the email, not as the source of the send.\nA DE created by applying a Data Filter to another DE - point-and-click segmentation without SQL. Example: \"subscribers from Master_DE where MemberTier = Gold\" produces a Gold-only Filtered DE.\nImportant: Filtered DEs need to be refreshed to reflect the current state of the source DE. They don't auto-update.\nRefresh via:\nIf the source DE changes (new imports, updates) but the Filtered DE isn't refreshed, the Filtered DE holds stale data. Campaigns targeting it send to outdated segments.\nFor anything more complex than single-attribute filtering (joins, calculations), use SQL Query Activity writing to a standard DE, not a Filtered DE.\nSplits a source DE into N equal random chunks. Use case: A/B/N testing where you need 10 equal groups to test 10 email variants.\nNo SQL needed. Configure the split percentages in the UI; SFMC assigns rows randomly.\nCaveats:\nA DE placed in the Shared Data Extensions folder in the parent Business Unit. Multiple child BUs in the Enterprise account can access the DE without copying it.\nUse when:\nAccess permissions are set via Shared Data Extension Permissions - which BUs can read/write.\nWatch for unintended cross-BU writes: if two BUs can write to the same Shared DE, coordinate schemas and import schedules.\nA special DE that logs every email send - who received what, when, subject line, etc. Useful for:\nCreated from the TriggeredSendDataExtension template when used with Triggered Sends.\nCaveat: Test Sends don't write to Send Log. Only production sends do. If you're testing and expecting the Send Log to populate, it won't.\nAny DE can have a retention policy configured on creation:\nUse for:\nSet retention at creation if possible. Adding it later works but doesn't apply retroactively to existing rows until the next automation evaluation.\nNeedDE TypeSend email from this listSendableReference data AMPscript will look upLookupSimple attribute-based segmentFilteredA/B test random splitsRandomCross-BU shared referenceSharedAudit / custom trackingSend LogAuto-purge old dataDE with Retention Policy\nMost projects end up with a mix: one or two Sendable DEs, several Lookup DEs, possibly a Shared DE for multi-brand setups, and retention policies on anything transient.\nNaming the DE type right in your head before creating it prevents architecture rebuilds. The decision takes seconds; fixing an incorrectly-typed DE after it's been loaded with data can take a day.\nDesigning SFMC data architecture? Our Salesforce team ships Data Extension layouts, shared-BU patterns, and retention strategies on production engagements. Get in touch ->\nSee our full platform services for the stack we cover.", "url": "https://wpnews.pro/news/seven-types-of-data-extensions-we-use-on-sfmc-projects", "canonical_source": "https://dev.to/sapotacorp/seven-types-of-data-extensions-we-use-on-sfmc-projects-83o", "published_at": "2026-05-24 02:52:26+00:00", "updated_at": "2026-05-24 03:01:24.912140+00:00", "lang": "en", "topics": ["data", "enterprise-software"], "entities": ["SFMC", "AMPscript", "Data Extension", "Filtered DE", "SQL Query Activity"], "alternates": {"html": "https://wpnews.pro/news/seven-types-of-data-extensions-we-use-on-sfmc-projects", "markdown": "https://wpnews.pro/news/seven-types-of-data-extensions-we-use-on-sfmc-projects.md", "text": "https://wpnews.pro/news/seven-types-of-data-extensions-we-use-on-sfmc-projects.txt", "jsonld": "https://wpnews.pro/news/seven-types-of-data-extensions-we-use-on-sfmc-projects.jsonld"}}