-- Script-1 :
SELECT
SCHEMA_NAME(schema_id) AS SchemaName
,Name AS TableName
FROM sys.objects
WHERE [type]='U'
AND object_id NOT IN
(
SELECT parent_object_id FROM sys.objects
WHERE [type]='PK'
)
GO
-- Script-2 :
SELECT
SCHEMA_NAME(schema_id) AS SchemaName
,Name AS TableName
FROM sys.tables
WHERE OBJECTPROPERTY(object_id,'TableHasPrimaryKey') = 0
GO