SQL Server: Get table primary key using sql query

Using SQL SERVER 2005, you can try

SELECT  i.name AS IndexName,
        OBJECT_NAME(ic.OBJECT_ID) AS TableName,
        COL_NAME(ic.OBJECT_ID,ic.column_id) AS ColumnName
FROM    sys.indexes AS i INNER JOIN 
        sys.index_columns AS ic ON  i.OBJECT_ID = ic.OBJECT_ID
                                AND i.index_id = ic.index_id
WHERE   i.is_primary_key = 1

Found at SQL SERVER – 2005 – Find Tables With Primary Key Constraint in Database

Found another one:

SELECT 
     KU.table_name as TABLENAME
    ,column_name as PRIMARYKEYCOLUMN
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS AS TC 

INNER JOIN INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS KU
    ON TC.CONSTRAINT_TYPE = 'PRIMARY KEY' 
    AND TC.CONSTRAINT_NAME = KU.CONSTRAINT_NAME 
    AND KU.table_name='YourTableName'

ORDER BY 
     KU.TABLE_NAME
    ,KU.ORDINAL_POSITION
; 

I have tested this on SQL Server 2003/2005

I also found another one for SQL Server:

SELECT COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE OBJECTPROPERTY(OBJECT_ID(CONSTRAINT_SCHEMA + '.' + QUOTENAME(CONSTRAINT_NAME)), 'IsPrimaryKey') = 1
AND TABLE_NAME = 'TableName' AND TABLE_SCHEMA = 'Schema'