一、MySQL Update Join 语法 以下是 UPDATE JOIN 语句将记录修改到 MySQL 表中的基本语法: UPDATE Tab1, Tab2, [INNER JOIN | LEFT JOIN] Tab1 ON Tab1.C1 =Tab2.C1 SET Tab1.C2= Tab2.C2, Tab2.C3 =expression WHERE Condition; 在上面的 MySQL UPDATE JOIN 语法中: 首先,我们在 UPDATE 子句之后...
salaryFLOATDEFAULTNULL,PRIMARYKEY (emp_id),CONSTRAINTfk_performanceFOREIGNKEY (performance)REFERENCESmerits (performance) );-- insert data for merits tableINSERTINTOmerits(performance,percentage)VALUES(1,0), (2,0.01), (3,0.03), (4,0.05), (5,0.08);-- insert data for employees tableINSERTINTOemp...
create table test_record_lock( id int not null comment '主键', age int null comment '年龄,普通索引', name varchar(10) null comment '姓名,无索引', constraint test_record_lock_pk primary key (id)) comment '测试记录锁';create index test_record_lock_age_index on test_record_lock (age);...
在新增表之后增加外键:修改表结构 alter table 表名 add [constraint 外键名字] foreign key(外键字段) references 父表(主键字段) -- 创建表 create table my_foreign2( id int primary key auto_increment, name varchar(20) not null comment '学生姓名', c_id int comment '班级id' -- 普通字段 )char...
mysql> insert into t_user values (3,'maiqi',3); //参照完整性测试,不能插入在主表中不存在的外键值 ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`test`.`t_user`, CONSTRAINT `t_user_ibfk_1` FOREIGN KEY (`groupid`) REFERENCES `t_group` (...
PGsql 也有类似于mysql ON DUPLICATE KEY UPDATE 的语法 注意,ON CONFLICT 只在 PostgreSQL 9.5 以上可用。...这就是为什么将其称为 upsert(update or insert)的原因。...其中的 constraint_name 可以是一个唯一约束的名字 WHERE predicate:带谓语的 WHERE 子句 action 可以是: DO NOTHING:当记录存在时,什么都...
Mysql错误1452 – Cannot add or update a child row: a foreign key constraint fails 原因及解决方法[通俗易懂] 大家好,又见面了,我是你们的朋友全栈君。 报错的原因大概分为三种: 原因一: 添加的外键列与另一个表的唯一索引列(一般是主键)的数据类型不同原因...
Server and Status Variables and Options Added, Deprecated, or Removed in MySQL 8.4 since 8.0 How to Report Bugs or Problems MySQL Standards Compliance MySQL Extensions to Standard SQL MySQL Differences from Standard SQL SELECT INTO TABLE Differences UPDATE Differences FOREIGN KEY Constraint Differe...
mysql> insert into t_user values (3,'maiqi',3); //参照完整性测试,不能插入在主表中不存在的外键值 ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`test`.`t_user`, CONSTRAINT `t_user_ibfk_1` FOREIGN KEY (`groupid`) REFERENCES `t_group` (...
CONSTRAINT fk_performance FOREIGN KEY (performance) REFERENCES merits (performance) ); -- insert data for merits table INSERT INTO merits(performance,percentage) VALUES(1,0), (2,0.01), (3,0.03), (4,0.05), (5,0.08); -- insert data for employees table ...