Oracle sdo_nn Update センテンスで一意の結果が 1 つだけ必要です。

明らかに、できません (簡略化)

set t1.fieldA = (t2.fieldB, distance)  --> you want to put two values into a single column

したがって、fieldB を取得します。 分析関数を使用するサブクエリから単独で (row_number ) sdo_nn_distance(1) desc で行を「並べ替える」;次に、最初の行の fieldB を取得します

このようなもの (括弧を正しく設定できれば幸いです):

UPDATE table1 t1
   SET t1.fieldA =
          (SELECT x.fieldB                                 --> only fieldB
             FROM (SELECT T2.fieldB,                       --> from your subquery
                          SDO_NN_DISTANCE (1) distance,
                          ROW_NUMBER ()
                             OVER (ORDER BY sdo_nn_distance (1) DESC) rn
                     FROM table1 T1, table2 T2
                    WHERE (sdo_nn (t1.geometry,
                                   t2.geometry,
                                   'SDO_NUM_RES=1',
                                   1) = 'TRUE')) x
            WHERE rn = 1)                                  --> where RN = 1
 WHERE EXISTS
          (SELECT 1
             FROM table2 t2
            WHERE     sdo_nn (t1.geometry,
                              t2.geometry,
                              'SDO_NUM_RES=1',
                              1) = 'TRUE'
                  AND (   t2.cell_name = 'string1'
                       OR t2.cell_name = 'string2')
                  AND t1.fieldA IS NULL);