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docs(config): derived variables in the EDIT screen #21

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allan merged 23 commits from docs/derived-variables into main 2026-10-21 22:26:31 +00:00
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@@ -6,7 +6,7 @@ description: Derived variables are computed columns that appear in the EDIT scre
# Derived Variables
A derived variable is a column that does not exist in the target table, but is computed when the table is loaded into the [EDIT screen](/dc-userguide/#edit). It is read-only, it appears after the physical columns, and it can be filtered on like any other column.
A derived variable is a column that does not exist in the target table, but is computed when the table is loaded into the [EDIT screen](/dc-userguide/#editor). It is read-only, it appears after the physical columns, and it can be filtered on like any other column.
Derived variables are useful when users need to work with a value that is a function of the stored data - a banding, a concatenation, a calculation - without changing the table, the load process, or the ETL.
@@ -52,11 +52,13 @@ The type and length are declared, not inferred, so a value is truncated exactly
The derived variable is created before the filter is applied, so it can be used in the [filter](/filter/) like any other column - including its list of values. A filter on a derived column is stored and re-applied in the normal way, and the value list for a derived column is built from the table under the rest of the filter, exactly as for a stored column.
Derived columns themselves are an EDIT screen feature: the VIEW screen and the download services do not show them. A saved filter that references a derived column still applies there, and is evaluated the same way.
## Rules and limits
- **Expressions only.** `VARIABLE_LOGIC` must be a single SAS expression - no semicolons, macro triggers (`%`, `&`) or comments. Conditional logic is available through functions such as `ifc()`, `choosec()`, `cats()`, `catx()`, `put()`, `input()` and `intnx()`.
- **Self-contained.** An expression may reference the columns of the target table only, not another derived variable. Derived variables are evaluated independently of each other.
- **No collisions.** `VARIABLE_NM` must not match an existing column of the target table, or one of the reserved names (`TX_FROM`, `TX_TO`, `PROCESSED_DTTM`, `_____DELETE__THIS__RECORD_____`).
- **No collisions.** `VARIABLE_NM` must not match an existing column of the target table, or one of the reserved names (`TX_FROM`, `TX_TO`, `PROCESSED_DTTM`, `VAR_TXFROM`, `VAR_TXTO`, `VAR_PROCESSED`, `_____DELETE__THIS__RECORD_____`).
- **Read-only.** Derived columns cannot be edited in the grid, and any value submitted for them is discarded before the approval package is created.
- **Recomputed on every read.** The value always reflects the current data and the current definition, and there is no history of previous derived values.