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The impact of different validation rules on the database
create database
Let's first look at the syntax for database creation:
CREATE DATABASE [IF NOT EXISTS] db_name [create_specification [, create_specification] ...] create_specification: [DEFAULT] CHARACTER SET charset_name [DEFAULT] COLLATE collation_name
- capitalize keywords
- [] is optional
- CHARACTER SET: Specifies the character set used by the database
- COLLATE: Specifies the validation rule for the database character set
Let's take a look at the actual database created
//创建名为db1的数据库
create database db1;This creation does not specify the character set and validation rules used. The default character set is: utf8, and the validation rule is: utf8_general_ci.
Next, let's create two specific databases, ① a db2 database using the utf8 character set and ② a db3 database using the utf character set with collation rules.
create database db2 charset=utf8;
create database db3 charset=utf8 collate utf8_general_ci;The impact of different validation rules on the database
We can first use show collation to view the validation rules contained in the database
show collation;
Among them, utf8_general_ci and utf8_bin, the former is case-insensitive, and the latter is case-sensitive.
//使用校验规则utf8_general_ci(不区分大小写)
create database db1 collate utf8_general_ci;
use db1;
create table tb1(name varchar(20));//创建表tb1
insert into tb1 values('a');
insert into tb1 values('A');
insert into tb1 values('b');
//使用校验规则utf8_bin（区分大小写）
create database db2 collate utf8_bin;
use db2;
create table tb2(name varchar(20));
insert into tb2 values('a');
insert into tb2 values('A');Let's take a look at the two tables created above, tb1 and tb2.
manipulate database
//查看数据库 show databases;
//显示创建语句 show create database 数据库名；
//修改数据库语法 ALTER DATABASE db_name [alter_spacification [,alter_spacification]...] alter_spacification: [DEFAULT] CHARACTER SET charset_name [DEFAULT] COLLATE collation_name//将db1数据库字符集改成gbk alter database db1 charset=gbk;
//数据库删除 DROP DATABASE [IF EXISTS] db_ name;
