Schema: How do I show all the primary keys in a database?

SQL Server 
 
This query will return all of the primary keys, including those with multiple columns (and will return those in the order they are listed in the key definition): 
 

SELECT       T.TABLE_NAME,       T.CONSTRAINT_NAME,       K.COLUMN_NAME,       K.ORDINAL_POSITION   FROM       INFORMATION_SCHEMA.TABLE_CONSTRAINTS T      INNER JOIN      INFORMATION_SCHEMA.KEY_COLUMN_USAGE K      ON T.CONSTRAINT_NAME = K.CONSTRAINT_NAME   WHERE      T.CONSTRAINT_TYPE = 'PRIMARY KEY'       -- AND T.TABLE_NAME = 'table_name'  ORDER BY      T.TABLE_NAME,      K.ORDINAL_POSITION

 
You can also use the following methods: 
 

EXEC sp_pkeys '<tablename>'  EXEC sp_helpconstraint '<tablename>'

 
sp_pkeys will return a row for each column that participates in the primary key for <tablename>. The columns you are likely most interested in are COLUMN_NAME and PK_NAME. 
 
sp_helpconstraint will list all constraints for <tablename>, including foreign keys that reference the table. In the first recordset, there will only be a column called Object Name (kind of useless, since that's what you passed in). In the second resultset, there will be the following columns: constraint_type, constraint_name, and constraint_keys. 
 
Microsoft Access 
 
This code uses ADOX to iterate through all the primary keys: 
 

<%       Set conn = CreateObject("ADODB.Connection")       Set cat = CreateObject("ADOX.Catalog")       conn.Open "Provider=Microsoft.Jet.OLEDB.4.0;" & _           "Data Source=<path to db>"      Set cat.ActiveConnection = conn         Response.Write "<table border=1><tr>" & _          "<th>Table/Column</th>" & _          "<th>Key Name</th></tr>"        For Each tbl in cat.Tables           if left(tbl.Name, 4) <> "MSys" then              For Each key in tbl.Keys                   If key.Type = 1 Then                      For Each col in key.Columns                           Response.Write "<tr><td>" & tbl.Name & "." & _                               col.Name & "</td><td>" & _                               key.Name & "</td></tr>"                       Next                   End If               Next           End If      Next         Response.Write "</table>"        Set cat = Nothing       conn.Close : Set conn = Nothing   %>