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docs/dynamic-cell-dropdown.md

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+---
+layout: article
+title: Dynamic Cell Dropdown
+description: Configure SAS programs to determine exactly which values can appear within which cells in your Data Controller table!
+og_image:  img/cell_validation1.png
+---
+
+# Dynamic Cell Dropdown
+
+This is a simple, but incredibly powerful feature!  Configure a SAS process to run when clicking a particular cell.  Data Controller will send the *row* to SAS, and your SAS program can use the values in the row determine a *column* of values to send back - which will be used in the frontend selectbox.
+
+So if you'd like the user to only see products for a particular category, or ISIN's for a particular asset group, you can perform that easily.
+
+## Frontend Configuration
+
+Open the MPE_VALIDATIONS table and configure the library, table and column that should contain the selectbox.  In the RULE_TYPE column, enter either:
+
+* HARDSELECT_HOOK - The user entry MUST match the returned values
+* SOFTSELECT_HOOK - The user can view the list but type something else if they wish
+
+The RULE_VALUE column should contain the full path to the SAS Program, Viya Job or SAS 9 Stored process that you would like to execute.  If the value ends in ".sas" then it is assumed to be a SAS program on a directory, otherwise a SAS web service (STP or Viya Job).
+
+## Backend Configuration
+If creating a Stored Process, be sure to deselect the 'automatic SAS macros' - the presence of %stpbegin or %stpend autocall macros will cause problems with the Data Controller backend.
+
+You can write any SAS code you wish - you will receive a table called `work.source_row`, and you should create a table with one column named `work.dynamic_values`.  These are the values that will be subsequently returned to the dropdown in the cell that the user has seleected.
+
+Example code:
+
+```sas
+/**
+  @file
+  @brief dynamic cell dropdown for product code
+  @details The input table is simply one row from the
+  target table called "work.source_row".
+
+  Available macro variables:
+    @li MPELIB - The DC control library
+    @li LIBDS - The library.dataset being filtered
+    @li VARIABLE_NM - The column being filtered
+
+
+  <h4> Service Outputs </h4>
+  Output should be a single table called
+  "work.dynamic_values" in the format below.
+
+  |DISPLAY_VALUE:$|RAW_VALUE:??|
+  |---|---|
+  |$44.00|44|
+
+**/
+
+%dc_assignlib(READ,mylibref)
+proc sql;
+create table work.DYNAMIC_VALUES as
+  select distinct some_product as raw_value
+  from mylibref.my_other_table
+  where area in (select area from work.source_row)
+  order by 1;
+
+```
+
+This feature is used extensively in Data Controller to fetch tables specific to a library, or columns specific to a table:
+
+![](img/cell_validation1.png)
+