Question

我创建了一个Oracle序列，如下所示：

CREATE SEQUENCE TASK_ID_SEQ START WITH 1 INCREMENT BY 1 NOCACHE NOCYCLE;

我有一个数据库表TASK，如下所示：

TASK_ID nextval from TASK_ID_SEQ
TASK_DATE   SYSDATE
TASK_TYPE   <value fed from data>

如果TASK表中的TASK_TYPE尚未显示TASK中的日期，我需要插入新的TASK_DATE记录，否则请忽略它。

以下语法是否正确？

MERGE INTO TASK a
USING (SELECT b.task_date FROM TASK b) 
ON (a.task_type = b.task_type)
WHEN NOT MATCHED THEN
[INSERT INTO TASK]

或者它应该是：

MERGE INTO TASK a
USING (SELECT b.task_date FROM TASK b) 
ON (a.task_type = b.task_type)
WHEN MATCHED THEN
[]
WHEN MATCHED THEN
[INSERT INTO TASK]

我可以替代使用

MERGE INTO TASK USING (select 1 from DUAL) . . .

请建议。

Answer 1

您的商家规则表示DATE和TYPE匹配。所以你的代码有两个问题：

USING子句需要选择确定匹配所需的所有条件。
ON子句需要测试确定匹配所需的所有标准。

此外，如果您不需要更新现有记录，则可以省略WHEN MATCHED分支。所以你的MERGE语句应该是这样的：

merge into task 
using ( 
    select date '2017-05-08' as dt, 'BATTLE' as typ from dual union all
    select date '2017-05-08' as dt, 'JUGGLE' as typ from dual union all
    select date '2017-05-08' as dt, 'PLOT' as typ from dual ) q
on (task.task_date = q.dt
    and task.task_type = q.typ)
when not matched then 
    insert values (task_id_seq.nextval, q.dt, q.typ)
/

演示。鉴于这个起点......

SQL> select * from task;

   TASK_ID TASK_DATE  TASK_TYPE
---------- ---------- ----------
         1 2017-05-06 CLEAN
         2 2017-05-06 BATTLE
         3 2017-05-06 JUGGLE
         4 2017-05-07 JUGGLE
         5 2017-05-07 CLEAN
         6 2017-05-07 NAP
         7 2017-05-08 BATTLE

7 rows selected.
SQL>

...上面的MERGE应插入两行（数据源中的一行与现有行匹配）。

SQL> merge into task 
  2  using ( 
  3     select date '2017-05-08' as dt, 'BATTLE' as typ from dual union all
  4     select date '2017-05-08' as dt, 'JUGGLE' as typ from dual union all
  5     select date '2017-05-08' as dt, 'PLOT' as typ from dual ) q
  6  on (task.task_date = q.dt
  7     and task.task_type = q.typ)
  8  when not matched then 
  9     insert values (task_id_seq.nextval, q.dt, q.typ)
 10  /  

2 rows merged.

SQL> select * from task
  2  /

   TASK_ID TASK_DATE  TASK_TYPE
---------- ---------- ----------
         1 2017-05-06 CLEAN
         2 2017-05-06 BATTLE
         3 2017-05-06 JUGGLE
         4 2017-05-07 JUGGLE
         5 2017-05-07 CLEAN
         6 2017-05-07 NAP
         7 2017-05-08 BATTLE
         9 2017-05-08 JUGGLE
        10 2017-05-08 PLOT

9 rows selected.

SQL>

数据来源并不完全清楚。所以在上面的例子中，我使用DUAL生成了一组任务。如果你想要的是从昨天的集合为今天创建一组新的任务，USING子句将如下所示：

merge into task 
using ( 
    select trunc(sysdate) as dt, task_type as typ 
    from task
    where task_date = trunc(sysdate) - 1 ) q
on (task.task_date = q.dt
    and task.task_type = q.typ)
when not matched then 
    insert values (task_id_seq.nextval, q.dt, q.typ)
/

使用与此版本之前相同的起始数据，插入三行：

SQL> select * from task;

   TASK_ID TASK_DATE  TASK_TYPE
---------- ---------- ----------
         1 2017-05-06 CLEAN
         2 2017-05-06 BATTLE
         3 2017-05-06 JUGGLE
         4 2017-05-07 JUGGLE
         5 2017-05-07 CLEAN
         6 2017-05-07 NAP
         7 2017-05-08 BATTLE
        11 2017-05-08 CLEAN
        12 2017-05-08 JUGGLE
        13 2017-05-08 NAP

10 rows selected.

SQL>

根据条件在同一个表上使用Oracle MERGE

1 个答案: