Dtjytyk

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.

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

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

If I understand correctly you want to find which columns are referenced by the computed column.

One solution would be searching the definition in sys.computed_columns with CHARINDEX() for each column where the object_id matches

SELECT DISTINCT c.name, 
 cc.definition 
FROM sys.columns c
CROSS APPLY
(
SELECT definition from sys.computed_columns cc
WHERE c.object_id = cc.object_id
AND CHARINDEX(c.name,cc.definition) > 0
) as cc;

Quick test

--Create a heap table.
CREATE TABLE dbo.test(id int,
 val int);
-- add computed column on two columns.
ALTER TABLE dbo.test 
ADD computedcolumn as id + val;

-- add a column that is not part of any computed column.
ALTER TABLE dbo.test 
ADD bla int;

The query for one specific table

SELECT DISTINCT c.name, 
 cc.definition 
FROM sys.columns c
CROSS APPLY
(
SELECT definition from sys.computed_columns cc
WHERE c.object_id = cc.object_id
AND CHARINDEX(c.name,cc.definition) > 0
) as cc
where c.object_id = object_id('dbo.test');

Result

name definition
id ([id]+[val])
val ([id]+[val])