Michael J. Swart

I have trouble with procedures that use SELECT *. They are often not “Blue-Green safe“. In other words, if a procedure has a query that uses SELECT * then I can’t change the underlying tables can’t change without causing some tricky deployment issues. (The same is not true for ad hoc queries from the application).

I also have a lot of procedures to look at (about 5000) and I’d like to find the procedures that use SELECT *.
I want to maybe ignore SELECT * when selecting from a subquery with a well-defined column list.
I also want to maybe include related queries like OUTPUT inserted.*.

The Plan

1. So I’m going to make a schema-only copy of the database to work with.
2. I’m going to add a new dummy-column to every single table.
3. I’m going to use sys.dm_exec_describe_first_result_set_for_object to look for any of the new columns I created

Any of my new columns that show up, were selected with SELECT *.

The Script

use master;
DROP DATABASE IF EXISTS search_for_select_star;
DBCC CLONEDATABASE (the_name_of_the_database_you_want_to_analyze, search_for_select_star);
ALTER DATABASE search_for_select_star SET READ_WRITE;
GO
 
use search_for_select_star;
 
DECLARE @SQL NVARCHAR(MAX);
SELECT 
	@SQL = STRING_AGG(
		CAST(
			'ALTER TABLE ' + 
			QUOTENAME(OBJECT_SCHEMA_NAME(object_id)) + 
			'.' + 
			QUOTENAME(OBJECT_NAME(object_id)) + 
			' ADD NewDummyColumn BIT NULL' AS NVARCHAR(MAX)),
		N';')
FROM 
	sys.tables;
 
exec sp_executesql @SQL;
 
SELECT 
	SCHEMA_NAME(p.schema_id) + '.' + p.name AS procedure_name, 
	r.column_ordinal,
	r.name
FROM 
	sys.procedures p
CROSS APPLY 
	sys.dm_exec_describe_first_result_set_for_object(p.object_id, NULL) r
WHERE 
	r.name = 'NewDummyColumn'
ORDER BY 
	p.schema_id, p.name;
 
use master;
DROP DATABASE IF EXISTS search_for_select_star;

Update

Tom from StraightforwardSQL pointed out a nifty feature that Microsoft has already implemented.

Not sure here, but doesn't dm_sql_referenced_entities.is_select_all achieve the same thing?

— Zikato (@Zikato25) August 9, 2021

Yes it does! You can use it like this:

select distinct SCHEMA_NAME(p.schema_id) + '.' + p.name AS procedure_name
from sys.procedures p
cross apply sys.dm_sql_referenced_entities(
	object_schema_name(object_id) + '.' + object_name(object_id), default) re
where re.is_select_all = 1

Comparing the two, I noticed that my query – the one that uses dm_exec_describe_first_result_set_for_object – has some drawbacks. Maybe the SELECT * isn’t actually included in the first result set, but some subsequent result set. Or maybe the result set couldn’t be described for one of these various reasons

On the other hand, I noticed that dm_sql_referenced_entities has a couple drawbacks itself. It doesn’t seem to capture select statements that use `OUTPUT INSERTED.*` for example.

In practice though, I found the query that Tom suggested works a bit better. In the product I work most closely with, dm_sql_referenced_entities only missed 3 procedures that dm_exec_describe_first_result_set_for_object caught. But dm_exec_describe_first_result_set_for_object missed 49 procedures that dm_sql_referenced_entities caught!