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How to find if a column is referenced in a computed column?

Submitted by: @import:stackexchange-dba··
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computedreferencedhowcolumnfind

Problem

I'm trying to mass retype columns. That means first dropping and recreating any constraints they are part of.

I found columns referenced by these constraints

  • Foreign Keys,



  • Primary Keys,



  • Indexes,



  • Check constraints,



  • Rules,



  • Default constraints.



But I cannot find Computed columns.

I've looked into INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE, but it doesn't include Computed Columns.

There is also sys.computed_columns which shows definition, but doesn't list columns in searchable manner.

Is there anywhere else I can look? If SQL Server can figure out the dependence, I thought I would be able to as well.

Solution

Thanks to Scott Hodgin I found it in sys.sql_expression_dependencies

SELECT 
    OBJECT_NAME(sed.referencing_id)     AS referencingTable
    , pc.[name] AS computedColumn
    , pc.is_computed
    , cc.[name] AS referencedcolumn
    , cc.is_computed
FROM sys.sql_expression_dependencies sed
JOIN sys.[columns] pc ON sed.referencing_minor_id = pc.column_id AND sed.referencing_id = pc.[object_id]
JOIN sys.[columns] cc ON sed.referenced_minor_id = cc.column_id AND sed.referenced_id = cc.[object_id]
WHERE sed.referencing_minor_id > 0      -- referencing object is Column
AND sed.referenced_minor_id > 0         -- referenced object is Column
AND sed.referencing_id = sed.referenced_id  -- references the same table

Code Snippets

SELECT 
    OBJECT_NAME(sed.referencing_id)     AS referencingTable
    , pc.[name] AS computedColumn
    , pc.is_computed
    , cc.[name] AS referencedcolumn
    , cc.is_computed
FROM sys.sql_expression_dependencies sed
JOIN sys.[columns] pc ON sed.referencing_minor_id = pc.column_id AND sed.referencing_id = pc.[object_id]
JOIN sys.[columns] cc ON sed.referenced_minor_id = cc.column_id AND sed.referenced_id = cc.[object_id]
WHERE sed.referencing_minor_id > 0      -- referencing object is Column
AND sed.referenced_minor_id > 0         -- referenced object is Column
AND sed.referencing_id = sed.referenced_id  -- references the same table

Context

StackExchange Database Administrators Q#236660, answer score: 7

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