Problem
One design aspect that all tables should have is a primary key. The primary key is the main entry way into your dataset, so that when you access your data you are guaranteed to only affect one row of data. Having primary keys are not only a good design feature, but they also play an important role in replication and data updates especially when there may be duplicate rows of data. So how can you determine what tables have primary keys and what tables do not have primary keys?
Solution
As mentioned above, primary keys guarantee a unique row of data in your table. Some of the design aspects of a primary key are as follows:
- can be one or more columns
- column values can not be null
- the column or combination of columns must be unique
- there can only be one primary key on a table
There have been other tips that focus on all indexes that exist in the database, but here we will take a different look at tables that have primary keys and tables that do not have primary keys. For SQL 2005 and later this is pretty easy to do by using the sys.key_constraints catalog views, but with SQL 2000 it is a bit cryptic to get this information.
Find All SQL Server Tables in Database With a Primary Key
Here are scripts you can use to find all tables in a database that have a primary key.
SQL Server 2005 / 2008 / 2008 R2 / 2012 / 2014 / 2016 / 2017 / 2019 / 2022
SELECT
c.name as SchemaName,
b.name as TableName,
a.name as PKname
FROM sys.key_constraints a
INNER JOIN sys.tables b ON a.parent_object_id = b.OBJECT_ID
INNER JOIN sys.schemas c ON a.schema_id = c.schema_id
WHERE a.type = 'PK'
SQL Server 2000
SELECT c.name, a.name, b.name
FROM sysobjects a
INNER JOIN sysindexes b ON a.id = b.id
INNER JOIN sysusers c ON a.uid = c.uid
WHERE (b.status & 2048)<>0
Find All SQL Server Tables in Database Without a Primary Key
Here are scripts you can use to find all tables in a database that do not have a primary key.
SQL Server 2005 / 2008 / 2008 R2 / 2012 / 2014 / 2016 / 2017 / 2019 / 2022
SELECT
c.name as SchemaName,
b.name as TableName
FROM sys.tables b
INNER JOIN sys.schemas c ON b.schema_id = c.schema_id
WHERE b.type = 'U'
AND NOT EXISTS (SELECT a.name
FROM sys.key_constraints a
WHERE a.parent_object_id = b.OBJECT_ID
AND a.schema_id = c.schema_id
AND a.type = 'PK' )
SQL Server 2000
SELECT c.name, a.name
FROM sysobjects a
INNER JOIN sysusers c ON a.uid = c.uid
WHERE xtype = 'U'
AND NOT EXISTS (SELECT b.name
FROM sysindexes b
WHERE a.id = b.id
AND (b.status & 2048)<>0)
Next Steps
- Now that you have these queries take the time to identify where primary keys may be missing
- As a good design rule you should always create a primary key for all of your tables
- If you don’t have a good candidate for a primary key in your table then look at using an identity column just for this purpose
Greg Robidoux has been working with databases for 35+ years with extensive hands on SQL Server experience from version 6.5 to 2025. He has authored over 250 technical articles and delivered several presentations online and at various conventions. Greg is also the President and founder of Edgewood Solutions, a technology services company delivering services and solutions for Microsoft SQL Server.
