情報スキーマと主キー

SELECT  c.TABLE_NAME, c.COLUMN_NAME,c.DATA_TYPE, c.Column_default, c.character_maximum_length, c.numeric_precision, c.is_nullable
             ,CASE WHEN pk.COLUMN_NAME IS NOT NULL THEN 'PRIMARY KEY' ELSE '' END AS KeyType
FROM INFORMATION_SCHEMA.COLUMNS c
LEFT JOIN (
            SELECT ku.TABLE_CATALOG,ku.TABLE_SCHEMA,ku.TABLE_NAME,ku.COLUMN_NAME
            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
         )   pk 
ON  c.TABLE_CATALOG = pk.TABLE_CATALOG
            AND c.TABLE_SCHEMA = pk.TABLE_SCHEMA
            AND c.TABLE_NAME = pk.TABLE_NAME
            AND c.COLUMN_NAME = pk.COLUMN_NAME
ORDER BY c.TABLE_SCHEMA,c.TABLE_NAME, c.ORDINAL_POSITION