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SQL Server: sys.all_objects

sys.all_objects shows all schema scoped user defined objects and system objects.

Select user defined stored procedures

The following query returns user defined (non pre-installed) stored procedures:
select
   sch.name             schema_name,
   alo.name             object_name,
-- alo.parent_object_id,
   alo.type             object_type,
   alo.type_desc        object_type_desc,
   alo.create_date      create_dt,
   alo.modify_date      modif_dt,
   alo.principal_id     object_principal_id,
   sch.principal_id     schema_principal_id,
   alo.is_ms_shipped,
   alo.is_published,
   alo.is_schema_published
from
   sys.all_objects alo                                   join
   sys.schemas     sch on alo.schema_id = sch.schema_id
where
   is_ms_shipped <>  1                      and
   alo.type_desc  = 'SQL_STORED_PROCEDURE';
Github repository about-MSSQL, path: /administration/schemas/sys/objects/views/all_objects/select.sql

types

The types that are found in sys.all_objects seem be:
select
   type_desc,
   type
-- count(*)     cnt
from
   sys.all_objects
group by
   type_desc,
   type
order by
   type_desc;

--
-- type_desc                                                    type
-- ------------------------------------------------------------ ----
-- AGGREGATE_FUNCTION                                           AF
-- CHECK_CONSTRAINT                                             C
-- CLR_SCALAR_FUNCTION                                          FS
-- CLR_STORED_PROCEDURE                                         PC
-- CLR_TABLE_VALUED_FUNCTION                                    FT
-- DEFAULT_CONSTRAINT                                           D
-- EXTENDED_STORED_PROCEDURE                                    X
-- FOREIGN_KEY_CONSTRAINT                                       F
-- INTERNAL_TABLE                                               IT
-- PRIMARY_KEY_CONSTRAINT                                       PK
-- RULE                                                         R
-- SERVICE_QUEUE                                                SQ
-- SQL_INLINE_TABLE_VALUED_FUNCTION                             IF
-- SQL_SCALAR_FUNCTION                                          FN
-- SQL_STORED_PROCEDURE                                         P
-- SQL_TABLE_VALUED_FUNCTION                                    TF
-- SYNONYM                                                      SN
-- SYSTEM_TABLE                                                 S
-- TYPE_TABLE                                                   TT
-- UNIQUE_CONSTRAINT                                            UQ
-- USER_TABLE                                                   U
-- VIEW                                                         V
Github repository about-MSSQL, path: /administration/schemas/sys/objects/views/all_objects/types.sql
Microsoft's documentation also lists PG (Plan Guide), however, I was not (yet?) able to find such a thing.

Definition of all_objects

sp_helptext 'sys.all_objects' returns
CREATE VIEW sys.all_objects AS
	SELECT 
		o.name, o.id AS object_id, r.indepid AS principal_id,
		o.nsid AS schema_id, o.pid AS parent_object_id,
		convert(char(2), case o.type when 'ET' then 'U' else o.type end) AS type,
		n.name AS type_desc,
		o.created AS create_date, o.modified AS modify_date,
		convert(bit, o.status & 1) AS is_ms_shipped,        -- OBJALL_MSSHIPPED
		convert(bit, o.status & 16) AS is_published,        -- OBJALL_RPL_PUBLISHED
		convert(bit, o.status & 64) AS is_schema_published	-- OBJALL_RPL_PUB_SCHONLY
	FROM sys.sysschobjs$ o
	LEFT JOIN sys.syssingleobjrefs r ON r.depid = o.id AND r.class = 97 AND r.depsubid = 0	-- SRC_OBJOWNER
	LEFT JOIN sys.syspalnames n ON n.class = 'OBTY' AND n.value = o.type
	WHERE o.nsclass not in (20,21)        -- excluding DDL trigger
		AND HAS_ACCESS('AO', o.id) = 1

See also

The sys schema
SQL Server: comparison of object views

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