无法从SQL Server表中删除主键

Question

I have primary key for a table. I checked constraints by using below query.

 SELECT name
 FROM sys.key_constraints
 WHERE [type] = 'PK'
   AND [parent_object_id] = Object_id('<TableName>');

Output of above query: PK_dbo.TableName (only 1 constraint of entire table)

I am trying to drop above constraint by using below query.

 ALTER TABLE TableName DROP CONSTRAINT PK_dbo.TableName;

I tried as like below but same error.

 ALTER TABLE dbo.TableName DROP CONSTRAINT PK_dbo.TableName;

Query execution failed with error message :

Failed to execute query. Error: Incorrect syntax near '.'

What is wrong in above query?

Answer 1

Make sure you have the dot . in your constraint name.

If it is there, then type the constraint name inside square brackets, otherwise make sure you are giving the correct name

ALTER TABLE dbo.TableName DROP CONSTRAINT [PK_dbo.TableName];

Note : It is not recommended to use characters like dot, blank space etc in object names. Instead, use underscores like PK_dbo_TableName

Answer 2

It is because of the . in your primary key name. It can be avoided by using [ ] like this:

ALTER TABLE dbo.TableName DROP CONSTRAINT [PK_dbo.TableName];