删除未指定名称的外键的存储过程

数据库中的某个表A,因为业务原因被移到别的库。麻烦的是,有几张子表(B, C, D等)建有指向它的外键,而且在创建时没有指定统一的外键名。如此一来,在不同的环境(开发、测试、生产等)中该外键的名称不一样,必须逐个去查询外键名再进行删除,十分不便。

为此,特地编写了一个存储过程,只须指定子表名(B,C,D)和外键的列名,直接调用该存储过程即可。

Oracle的存储过程代码如下:

-- 删除指定表、指定列上的外键(系统命名或未知名)
CREATE OR REPLACE PROCEDURE DROP_FK(P_TABLE IN VARCHAR2, P_COLUMN IN VARCHAR2)
AS
   v_fk varchar2(100);
   v_sql varchar2(1000);
BEGIN
  SELECT A.CONSTRAINT_NAME INTO v_fk FROM USER_CONS_COLUMNS A, USER_CONSTRAINTS B
  WHERE  A.TABLE_NAME=UPPER(P_TABLE) AND A.COLUMN_NAME=UPPER(P_COLUMN)
    AND B.TABLE_NAME=UPPER(P_TABLE) AND B.CONSTRAINT_TYPE='R'
    AND A.CONSTRAINT_NAME=B.CONSTRAINT_NAME;
  v_sql := 'ALTER TABLE '|| P_TABLE ||' DROP CONSTRAINT '|| v_fk;
  EXECUTE IMMEDIATE v_sql;
EXCEPTION
  WHEN OTHERS THEN
    DBMS_OUTPUT.PUT_LINE('发生错误'||SQLCODE||''||SQLERRM);
END DROP_FK;
/

PostgreSql的代码如下:

-- 删除指定表、指定列上的外键(系统命名或未知名)
CREATE OR REPLACE FUNCTION DROP_FK(P_TABLE IN VARCHAR, P_COLUMN IN VARCHAR)
RETURNS void AS $$
   DECLARE v_fk  VARCHAR(100);
   DECLARE v_sql VARCHAR(1000);
BEGIN
   SELECT tc.constraint_name INTO v_fk
   FROM information_schema.table_constraints AS tc, information_schema.key_column_usage AS kcu 
   WHERE tc.table_name = lower(P_TABLE) AND kcu.column_name=lower(P_COLUMN)
     AND constraint_type = 'FOREIGN KEY' AND tc.constraint_name = kcu.constraint_name;
  v_sql := 'ALTER TABLE '|| P_TABLE ||' DROP CONSTRAINT '|| v_fk;
  EXECUTE v_sql;
EXCEPTION
  WHEN OTHERS THEN
    RAISE EXCEPTION '(%)', SQLERRM;
END;
$$ LANGUAGE plpgsql;

MySQL的代码如下:

DELIMITER //

DROP PROCEDURE IF EXISTS drop_fk//

-- 删除指定表、指定列上的外键(系统命名或未知名)
CREATE PROCEDURE drop_fk(IN P_TABLE VARCHAR(100), IN P_COLUMN VARCHAR(100)) LANGUAGE SQL
BEGIN
   DECLARE v_fk  VARCHAR(100);
   DECLARE v_sql VARCHAR(1000);
   DECLARE v_cnt INT;
   
   SELECT count(*) INTO v_cnt
   FROM information_schema.table_constraints TC, information_schema.key_column_usage TCU
   WHERE TC.TABLE_NAME=LOWER(P_TABLE) AND TCU.TABLE_NAME=LOWER(P_TABLE)
      AND CONSTRAINT_TYPE = 'FOREIGN KEY' AND COLUMN_NAME=LOWER(P_COLUMN) 
      AND TC.CONSTRAINT_NAME=TCU.CONSTRAINT_NAME;
   IF v_cnt=1 THEN
      SELECT TC.CONSTRAINT_NAME INTO v_fk
      FROM information_schema.table_constraints TC, information_schema.key_column_usage TCU
      WHERE TC.TABLE_NAME=LOWER(P_TABLE) AND TCU.TABLE_NAME=LOWER(P_TABLE)
         AND CONSTRAINT_TYPE = 'FOREIGN KEY' AND COLUMN_NAME=LOWER(P_COLUMN) 
         AND TC.CONSTRAINT_NAME=TCU.CONSTRAINT_NAME;
      SET v_sql = CONCAT('ALTER TABLE ', P_TABLE, ' DROP FOREIGN KEY ', v_fk);
      SET @sql = v_sql;
      PREPARE stmt FROM @sql;
      EXECUTE stmt;
      DEALLOCATE PREPARE  stmt;
   END IF;
END;
//

DELIMITER ;

 

posted @ 2019-05-07 16:04  闻歌感旧  阅读(327)  评论(0编辑  收藏  举报