标签：tab not where 主键 asc add color int str
创建表1
mysql> CREATE TABLE C( -> -> id TINYINT PRIMARY KEY auto_increment, -> name VARCHAR (20), -> age INT , -> is_marriged boolean -- show create table ClassCharger: tinyint(1) -> -> );
添加表1数据
mysql> INSERT INTO C (name,age,is_marriged) VALUES ("冰冰",12,0), -> ("丹丹",14,0), -> ("歪歪",22,0), -> ("姗姗",20,0), -> ("小雨",21,0);
创建表2 并把子键和主键建立关联并添加级联删除
mysql> CREATE TABLE S3( -> id INT PRIMARY KEY auto_increment, -> name VARCHAR (20), -> charger_id TINYINT, -> FOREIGN KEY (charger_id) REFERENCES C(id) ON DELETE CASCADE -> );
添加表2数据
mysql> INSERT INTO S3(name,charger_id) VALUES ("alvi1",2), -> ("alvi2",4), -> ("alvi3",5), -> ("alvi4",3), -> ("alvi5",5), -> ("alvi6",3), -> ("alvi7",2);
未删除前数据
mysql> SELECT * from S3; +----+-------+------------+ | id | name | charger_id | +----+-------+------------+ | 1 | alvi1 | 2 | | 2 | alvi2 | 4 | | 3 | alvi3 | 5 | | 4 | alvi4 | 3 | | 5 | alvi5 | 5 | | 6 | alvi6 | 3 | | 7 | alvi7 | 2 | +----+-------+------------+
mysql> select * from C; +----+------+------+-------------+ | id | name | age | is_marriged | +----+------+------+-------------+ | 1 | 冰冰 | 12 | 0 | | 2 | 丹丹 | 14 | 0 | | 3 | 歪歪 | 22 | 0 | | 4 | 姗姗 | 20 | 0 | | 5 | 小雨 | 21 | 0 | +----+------+------+-------------+
输入删除语句
mysql> delete from C where id = 4;
删除后表数据
mysql> select * from s3; +----+-------+------------+ | id | name | charger_id | +----+-------+------------+ | 1 | alvi1 | 2 | | 3 | alvi3 | 5 | | 4 | alvi4 | 3 | | 5 | alvi5 | 5 | | 6 | alvi6 | 3 | | 7 | alvi7 | 2 | +----+-------+------------+ 6 rows in set (0.00 sec)
mysql> select * from C; +----+------+------+-------------+ | id | name | age | is_marriged | +----+------+------+-------------+ | 1 | 冰冰 | 12 | 0 | | 2 | 丹丹 | 14 | 0 | | 3 | 歪歪 | 22 | 0 | | 5 | 小雨 | 21 | 0 | +----+------+------+-------------+
------set null方式 在父表上update/delete记录时，将子表上匹配记录的列设为null -- 要注意子表的外键列不能为not null
先删除之前在s3的外键
mysql> ALTER TABLE s3 DROP FOREIGN KEY s3_ibfk_1;
添加set null方式
mysql> alter table s3 add constraint s3_fk_cc foreign key (charger_id) -> references c(id) on delete set null;
查看表记录
mysql> select * from s3; +----+-------+------------+ | id | name | charger_id | +----+-------+------------+ | 1 | alvi1 | 2 | | 3 | alvi3 | 5 | | 4 | alvi4 | 3 | | 5 | alvi5 | 5 | | 6 | alvi6 | 3 | | 7 | alvi7 | 2 | +----+-------+------------+
mysql> select * from C; +----+------+------+-------------+ | id | name | age | is_marriged | +----+------+------+-------------+ | 1 | 冰冰 | 12 | 0 | | 2 | 丹丹 | 14 | 0 | | 3 | 歪歪 | 22 | 0 | | 5 | 小雨 | 21 | 0 | +----+------+------+-------------+
删除c表jilu
mysql> delete from C where id = 3;
s3表记录变为null
mysql> select * from s3; +----+-------+------------+ | id | name | charger_id | +----+-------+------------+ | 1 | alvi1 | 2 | | 3 | alvi3 | 5 | | 4 | alvi4 | NULL | | 5 | alvi5 | 5 | | 6 | alvi6 | NULL | | 7 | alvi7 | 2 | +----+-------+------------+
------Restrict方式 :拒绝对父表进行删除更新操作(了解) ------No action方式 在mysql中同Restrict,如果子表中有匹配的记录,则不允许对父表对应候选键 -- 进行update/delete操作（了解）
标签：tab not where 主键 asc add color int str
原文地址：https://www.cnblogs.com/hb15988111121/p/12804794.html
