I need only one unique result in Oracle sdo_nn Update sentence , - oracle11g

Question

I need Only one unique result from tableB.Field to tableA.Field
I am using sdo operator sdo_nn, this is the code:
UPDATE table1 t1
SET t1.fieldA = (SELECT T2.fieldB,SDO_NN_DISTANCE(1) distance
FROM table1 T1, table2 T2
WHERE
(sdo_nn(t1.geometry,t2.geometry,'SDO_NUM_RES=1',1)= 'TRUE')
ORDER BY DIST
)
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 = NULL
);
In the select sentence of the subquery i get an error because i only use one field(t1.fieldA), but in the sentence i use the operator SDO_NN_DISTANCE(1) and the sql developer count this operator like another field. What is the correct way to write this sentence? I only use sql because i need to insert this code in vba
Thanks!!!

Answer 1

Obviously, you can't (simplified)
set t1.fieldA = (t2.fieldB, distance) --> you want to put two values into a single column
Therefore, get fieldB alone from the subquery which uses analytic function (row_number) to "sort" rows by sdo_nn_distance(1) desc; then get the first row's fieldB value.
Something like this (I hope I set the parenthesis right):
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);