Oracle - 合併子查詢減少

Question

我有一個MERGEsubquery獲取和ID，我想知道subquery in the NOT MATCHED statement總是執行或不。

 MERGE INTO CAR_STOCK st 
     USING CAR_PRODUCTO pro 
     ON (pro.id = st.producto_id AND pro.ean = ?) 
     WHEN MATCHED THEN 
     UPDATE SET st.stockActual = ? 
     WHEN NOT MATCHED THEN 
     INSERT (stockActual, local_id, producto_id, activo) 
     VALUES (?, ?, (SELECT id FROM car_producto WHERE ean = ?), 'S'); 

謝謝！

編輯：?是因爲我在PreparedStatement使用JDBC。

Answer 1

無需子查詢，你可以簡單地指pro.id在insert一部分，就像這裏：

merge into t1 using t2 on (t1.a = t2.a) 
    when matched then update set t1.b = t2.b 
    when not matched then insert (a, b) 
    values (0, t2.b) 

---

測試數據和merge結果：

create table t1 as (select 1 a, 'a01' b from dual); 
create table t2 as (select 1 a, 'a05' b from dual union all select 2 a, 'bxx' b from dual); 

    A B 
------ --- 
    1 a05 
    0 bxx