MySQL增删改查的常用操作指令总结

时间:2022-06-29 10:22:04
总结:
1、数据库操作:
创建库:
create database db_name; 查询库:
show databases; //显示所有的数据库
show create databases db_name; //显示特定的数据库 删除库:
drop database db_name; 修改库:
alter database db_name [modify command];
alter database db_name character set gbk; 2、表操作:
创建表:
use db_name;
create table tbl_name (column_structure) [tbl_option];
如:
create table tbl_name(
variable_name1 varchar(10)
variable_name2 int
);
或 create table db_name.tbl_name(
variable_name1 varchar(10)
variable_name2 int
); 查询表:
查看有哪些表:
show tables;
或show tables like 'pattern_%';
查看表的创建信息:
show create table tbl_name;
或show create table tbl_name \G
查看表的结构:
describe tbl_name;
或desc tbl_name;] 删除表:
drop table [if exists] tbl_name; 修改表:
修改表名:
单个:rename table old_tbl_name to new_tbl_name;
多个:rename table old_tbl_name1 to new_tbl_name1, old_tbl_name2 to new_tbl_name2;
跨数据库:rename table old_tbl_name to db_name.new_tbl_name;
修改列定义:
增加新列定义:add
alter table tbl_name add new_column_name data_type;
如alter table exam_student add height int;
修改列的定义(新的属性或者数据类型):modify
alter table tbl_name modify column_name new_data_type;
删除一个列:drop
alter table tbl_name drop column_name;
重命名一个列:change
alter table tbl_name change old_column_name new_column_name new_data_type;
修改表选项:
alter table tbl_name new_tbl_option;
alter table tbl_name character set utf8; 3、数据操作:
创建数据:
insert into tbl_name (fields_list) values (values_list);
如:insert into exam_student (stu_name, stu_no) values ('xiaoming', 'php030_01');
若插入所有字段值:
insert into exam_student values ('xiaoming', 'php030_01', 98); 查询数据:
查看字段信息:
select * from tbl_name;
参看具体字段列表信息:
select fields_list from tbl_name where condition;
如:默认状态下select stu_name, stu_no from exam_student;
或:select stu_name, stu_no from exam_student where 1;
有条件查询:
select * from tbl_name where condition;
如select * from exam_student where fenshu >= 60; 删除数据:
delete from tbl_name condition;
如delete from exam_student where fenshu <= 50; 修改数据:
update tbl_name set field = new_value where condition;
如:update exam_student set fenshu =100 where fenshu >= 97; 4、主键:primary
如:法一:
create table teacher(
t_id int primary key [auto_increment],
t_name varchar(5),
class_name varchar(6),
t_days tinyint unsigned
);
法二:
create table teacher(
t_id int,
t_name varchar(5),
class_name varchar(6),
t_day tinyint unsigned,
primary key (t_id)
);
insert into teacher values (1, '王老师', '0225', 23);
自动增长:auto_increment
alter table tbl_name auto_increment initial_value; 5、外键:foreign key
如:
主表:
create table itcast_class(
class_id int primary key auto_increment,
class_name varchar(10) not null default 'itcast_php' comment '班级名称'
) character set utf8;
从表:
create table itcast_student(
stu_id int primary key auto_increment,
stu_name varchar(10) not null default '',
class_id int,
foreign key (class_id) references itcast_class (class_id)
) character set utf8;
插入数据的顺序:先主表,后从表
insert into itcast_class values (null, 'php0331');
insert into itcast_student values (null, '张三', 1);
删除操作:
alter table itcast_student drop foreign key itcast_student_ibfk_1;
alter table itcast_student add foreign key (class_id) references itcast_class (class_id)
on delete set null;/*主表里删除某个字段,从表若对应外键则变成null*/
或者
on delete cascade;/*主表删除一个字段,从表对应的外键则会删除相应的值*/
又或者
on update restrict;/*不允许主表进行更新操作*/
delete from itcast_class where class_id = 1;