与触发器相关的问题

Question

我的要求是：有两个表：a）C_Table，b）Mst_Table

两者具有相同的表结构，具有三列：i）S_NO，ii）CONTENT_ID，iii）INSTANCES

Mst_Table 最初有三个记录：

INSERT INTO Mst_Table Values (1, 'A1', 20);    
INSERT INTO Mst_Table Values (2, 'A2', 10);    
INSERT INTO Mst_Table Values (3, 'A3', 5);  

现在，我在表 C_table 中插入四条记录：

INSERT INTO C_Table Values (1, 'A1', 22);    
INSERT INTO C_Table Values (2, 'A4', 20);    
INSERT INTO C_Table Values (3, 'A5', 5);    
INSERT INTO C_Table Values (4, 'A1', 18);   

当记录插入到表 C_table 中时，它应该检查列 - CONTENT_ID、Mst_Table 是否已经有任何记录。如果不是，则插入将在 C_table 中成功完成，但如果是，则它将检查列 - INSTANCES。

如果C_Table 的INSTANCES 值大于Mst_Table，则在INSTANCES 列的C_table 值中应使用(INSTANCES_Value_C_Table - INSTANCES_Value_Mst_Table) 值进行更新。

触发器定义：

create or replace trigger ANALYTICS_UPDATE_COUNT 
    after insert on C_Table referencing old as old new as new 
    for each row 

    DECLARE -- variable declarations 
    v_instance number; 
    v_count number; 

BEGIN 
    insert into temp_logger (log_text) 
    values ('-------------BEGIN-------------'); 

    -- trigger code 
    BEGIN 
         select distinct INSTANCES 
         into v_instance 
         from Mst_Table 
         where CONTENT_ID = :new.CONTENT_ID; 

    EXCEPTION 
          WHEN OTHERS 
              THEN 
                NULL; 
    END; 

    insert into temp_logger (log_text) values ('Count for ' || :new.CONTENT_ID|| ' is : '|| v_instance); 
    insert into temp_logger (log_text) values ('Difference between new and existing: ' || (:new.INSTANCES - v_instance)); 

    if ((:new.INSTANCES - v_instance) <=0 ) then 
        v_count := 0; 
    else 
        v_count := (:new.INSTANCES - v_instance); 
    end if; 

    insert into temp_logger (log_text) values ('v_count variable: ' ||v_count); 

    if v_count = 0 then 
        insert into temp_logger (log_text) values ('Inside IF'); 
        DELETE from C_Table where CONTENT_ID = :new.CONTENT_ID; 
        COMMIT; 
    else 
        insert into temp_logger (log_text) values ('Inside ELSE'); 
        UPDATE C_Table 
        set INSTANCES = v_count 
        where CONTENT_ID = :new.CONTENT_ID; 

   COMMIT; 
    end if; 

EXCEPTION 
     WHEN OTHERS 
           THEN 
              NULL; 

END;

Answer 1

这是你的意图吗？

DROP TABLE Mst_Table
GO
DROP TABLE C_Table
GO

CREATE TABLE Mst_Table 
(
    S_NO int,
    CONTENT_ID varchar(2),
    INSTANCES int
)
GO
CREATE TABLE C_Table 
(
    S_NO int identity(1,1) not null,
    CONTENT_ID varchar(2),
    INSTANCES int
)
GO

 INSERT INTO Mst_Table Values (1, 'A1', 20);
 INSERT INTO Mst_Table Values (2, 'A2', 10);
 INSERT INTO Mst_Table Values (3, 'A3', 5); 
GO

CREATE TRIGGER VCTable ON C_Table
INSTEAD OF INSERT
AS
BEGIN
    INSERT INTO C_Table (CONTENT_ID, INSTANCES)
    SELECT inserted.CONTENT_ID, isnull(C_Table.INSTANCES - inserted.INSTANCES, inserted.INSTANCES)
    FROM inserted
    LEFT JOIN C_Table ON inserted.S_NO = C_Table.S_NO
    LEFT JOIN Mst_Table on inserted.CONTENT_ID = Mst_Table.CONTENT_ID   
END
GO

INSERT INTO C_Table (CONTENT_ID, INSTANCES) Values ('A1', 22);
INSERT INTO C_Table (CONTENT_ID, INSTANCES) Values ('A4', 20);
INSERT INTO C_Table (CONTENT_ID, INSTANCES) Values ('A5', 5);
INSERT INTO C_Table (CONTENT_ID, INSTANCES) Values ('A1', 18); 

SELECT * FROM C_Table