仅作记录,游标,级联删除,获取所有该外键的表名

      以下内容只是部分原创，仅是之前收集到的知识。只做记录避免遗忘,具体出处已遗忘。

一、游标结构

   总是遗忘游标的结构

declare  PeriodDataCursor cursor 
for 
select  ID  , ClassTime  from  @temptable  order by [ClassTime]  desc 
open  PeriodDataCursor 
fetch next from  PeriodDataCursor  into  @ID , @firstClsTime
while(@@FETCH_STATUS=0)
begin 
 if((select top 1 1 from Mall_EverydayValue where  Summary='-初始化'  and InPeriod=@ID )=1)
 begin
   select   1  ;
 end
fetch next from  PeriodDataCursor  into   @ID , @firstClsTime
end
 close  PeriodDataCursor
 deallocate  PeriodDataCursor
end  

二、级联删除,更新

  

/*  
   drop table  test_sub
   drop table  test_main
   
   */ 

-- 创建测试主表. ID 是主键.
CREATE TABLE test_main 
( 
 id      INT   NOT NULL,  
 value   VARCHAR(10),  PRIMARY KEY(id) 
 ); 
 
  
-- 创建测试子表.
 CREATE TABLE test_sub 
 (  id      INT  NOT NULL, 
  main_id INT ,  value   VARCHAR(10),  PRIMARY KEY(id)
 );
 
 --创建外键，使用 ON DELETE CASCADE 选项，删除主表的时候，同时删除子表
 --   ON UPDATE CASCADE  级联更新
 ALTER TABLE test_sub ADD CONSTRAINT main_id_cons FOREIGN KEY (main_id)  REFERENCES  test_main(id) 
  ON DELETE CASCADE   ON UPDATE CASCADE ;
 
    -- 插入测试主表数据.
    INSERT INTO test_main(id, value) VALUES (1, 'ONE');
    INSERT INTO test_main(id, value) VALUES (2, 'TWO'); 
    -- 插入测试子表数据.
    INSERT INTO test_sub(id, main_id, value) VALUES (1, 1, 'ONEONE');
    INSERT INTO test_sub(id, main_id, value) VALUES (2, 2, 'TWOTWO');

--执行删除：

DELETE FROM TEST_MAIN WHERE ID = 1;
-- 执行更新：
update  TEST_MAIN set id=5 from  TEST_MAIN where id=2 ;

--   DELETE FROM test_sub WHERE ID = 1;
--最后：

SELECT * FROM TEST_MAIN;
SELECT * FROM test_sub;
--结果子表中就只有ID=5的记录，也就说明级联删除成功和更新成功。

三、获取该所有外键

SELECT 主键列ID=b.rkey 
    ,主键列名=(SELECT name FROM syscolumns WHERE colid=b.rkey AND id=b.rkeyid) 
    ,外键表ID=b.fkeyid 
    ,外键表名称=object_name(b.fkeyid) 
    ,外键列ID=b.fkey 
    ,外键列名=(SELECT name FROM syscolumns WHERE colid=b.fkey AND id=b.fkeyid) 
    ,级联更新=ObjectProperty(a.id,'CnstIsUpdateCascade') 
    ,级联删除=ObjectProperty(a.id,'CnstIsDeleteCascade') 
FROM sysobjects a 
    join sysforeignkeys b on a.id=b.constid 
    join sysobjects c on a.parent_obj=c.id 
where a.xtype='f' AND c.xtype='U' 
    and object_name(b.rkeyid)='TEST_MAIN'