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备份单张表:
create table a ( id int auto_increment , name char(16), address char(128), primary key(id))insert into a(name,address) values ('aaa',null) , ('bbb',null)/* 先拷贝表结构, 再插入数据 */create table c like a ;insert into c select * from a ;/* 直接拷贝数据, 但是丢失了表a 的 primary key,,auto_increment等属性约束 */create table d select * from a ;
查看ddl如下:
CREATE TABLE c ( id INT NOT NULL AUTO_INCREMENT, name CHAR(16), address CHAR(128), PRIMARY KEY (id) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 DEFAULT COLLATE=utf8_general_ci;CREATE TABLE d ( id INT DEFAULT 0 NOT NULL, name CHAR(16), address CHAR(128) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 DEFAULT COLLATE=utf8_general_ci;
Mysql 更新字段来自于另一张表:
# update select 语句(注意:必须使用inner join)
# 语法 update a inner join (select yy from b) c on a.id =c.id set a.xx = c.yy例子:update a join b on a.name=b.name and b.status=1 set a.address=b.address
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