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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 ;
: