MYSQL

USE test;

DROP TABLE if EXISTS test5;
CREATE TABLE TEST5(
c1 datetime,
c2 TIMESTAMP,
c3 char(10)
);
insert into test5 VALUES(now(),CURRENT_TIMESTAMP,'布朗');//now() 计算当前的系统时间 CURRENT_TIMESTAMP 当前时间戳
INSERT into test5 VALUES('1999-05-01 10:10:10',CURRENT_TIMESTAMP,'Sun');
UPDATE test5 set c3='Dawn' where c3='布朗';
SELECT *from test5;

字符串类型

USE test;

DROP TABLE if EXISTS test6;
CREATE TABLE TEST6(
c1 char(4),
c2 VARCHAR(4)
)ENGINE=myisam;#存储引擎myisam
insert into test6 VALUES('ab','ab');
insert into test6 VALUES('lwy','lwy');
insert into test6 VALUES('','');
SELECT * FROM TEST6;

USE test;
DROP TABLE if EXISTS test7;
CREATE TABLE TEST7(
v varchar(4),
c CHAR(4)
);
insert into test7 VALUES('ab ','ab ');
SELECT CONCAT(v,'+'),CONCAT(c,'+') FROM test7;#CONCAT() 字符串连接函数

复合类型

USE test;
DROP TABLE if EXISTS test8;
CREATE TABLE TEST8(
c1 char(4),
c2 SET('Reading','basketball','shopping')NOT null,
c3 enum('male','female') NOT null
)ENGINE=myisam,charset=gbk;
insert INTO test8 VALUES('乔丹','basketball,shopping','male');
SELECT * from test8;

USE test;
DROP TABLE if EXISTS test9;
CREATE TABLE TEST9(
c1 int(11) auto_increment PRIMARY KEY,
c2 CHAR(10)
)ENGINE=myisam,charset=gbk,auto_increment=100;
INSERT into test9(1,'A');
INSERT into test9(6,'B');

保存路径
CREATE TABLE TEST9(
path VARCHAR(99)
);
INSERT into test10(D:\MySQL); //要使用双\

create table people(
id int not null primary key,
name varchar(20) not null,
sex char(1) default 'm' //默认值为m
);
insert into people(id,name)values(1,'chenxi');
insert into people values(2,'liwuyi');
select * from people;

唯一性约束的列可以有多个空值 因为null<>null

DESC(DESCRIBE) 表名; 描述表的结构

CREATE TABLE temp_pk(
id int,
name VARCHAR(20),
CONSTRAINT pk_id_name PRIMARY KEY(id,name) #组合键 CONSTRAINT 约束
);
DESC temp_pk ;#DESC=DESCRIBE 描述表的结构

重点：
CREATE TABLE student(
sno CHAR(10) PRIMARY KEY,
sname CHAR(10),
did INT,
FOREIGN KEY(did) REFERENCES sdept(did) #student表中的did列(外键约束)手sdept主表的did限制
);

show create table sdept; 显示表的信息