[英]How to implement AFTER INSERT Trigger in Oracle PL/SQL?
I am trying to implement after insert trigger in PLSQL.我正在尝试在 PLSQL 中插入触发器后实现。
The goal is to check if there are multiple (>1) rows having specific status for each client.目标是检查是否有多个 (>1) 行具有每个客户端的特定状态。
If so I'd like to rise an exception and roll the insertion back.如果是这样,我想引发异常并将插入回滚。
I am struggling with implementing warning-free query, which causes error during insertion.我正在努力实现无警告查询,这会在插入过程中导致错误。
How could I manage this?我怎么能做到这一点?
Here is my implemented trigger which I guess needs some changes.这是我实现的触发器,我想需要一些更改。
CREATE TRIGGER blatrigger
AFTER INSERT
ON BLATABLE
REFERENCING NEW AS NEW OLD AS OLD
FOR EACH ROW
DECLARE
exception_name EXCEPTION;
PRAGMA EXCEPTION_INIT (exception_name, -20999);
BEGIN
if (select count(*) as counter from BLATABLE where CLIENTID = :NEW.CLIENTID and STATUS='PENDING').counter > 1
THEN
raise exception_name;
END IF;
END;
Here is the table itself:这是表格本身:
create table BLATABLE
(
ID NUMBER(19) not null primary key,
CLIENTID NUMBER(10),
CREATED TIMESTAMP(6),
STATUS VARCHAR2(255 char)
);
The goal is to check if there are multiple (>1) rows having specific status for each client.
目标是检查是否有多个 (>1) 行具有每个客户端的特定状态。 If so I'd like to rise an exception and roll the insertion back.
如果是这样,我想引发异常并将插入回滚。
No need for a trigger.不需要触发器。 It looks like a simple unique constraint should get the job done here:
看起来一个简单的唯一约束应该在这里完成工作:
create table blatable (
id number(19) not null primary key,
clientid number(10),
created timestamp(6),
status varchar2(255 char),
constraint blaconstraint unique (clientid, status)
);
The unique constraint prevents duplicates on (clientid, status)
across the whole table.唯一约束可防止整个表中的
(clientid, status)
重复。 If a DML operation (insert, update) attempts to generate a duplicate, an error is raised and the operation is rolled back.如果 DML 操作(插入、更新)尝试生成重复项,则会引发错误并回滚该操作。
If, on the other end, you want to allow only one "PENDING" status per user, then you can use a unique index as follows:另一方面,如果您希望每个用户只允许一个“PENDING”状态,那么您可以使用唯一索引,如下所示:
create unique index bla_index
on blatable( (case when status = 'PENDING' then clientid end) );
Use a Statement Level Trigger, rather than a Row Level by removing FOR EACH ROW
, and converting to your code as below :通过删除
FOR EACH ROW
并转换为您的代码,使用语句级别触发器,而不是行级别,如下所示:
CREATE OR REPLACE TRIGGER blatrigger
AFTER INSERT ON BLATABLE
REFERENCING NEW AS NEW OLD AS OLD
DECLARE
counter INT;
exception_name EXCEPTION;
PRAGMA EXCEPTION_INIT(exception_name, -20999);
BEGIN
SELECT MAX(COUNT(*))
INTO counter
FROM BLATABLE
WHERE STATUS = 'PENDING'
GROUP BY CLIENTID;
IF counter > 1 THEN
RAISE exception_name;
END IF;
END;
/
where在哪里
IF .. THEN
conditional IF .. THEN
条件中删除
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