[打卡]13113113

create DATABASE aaa;
use aaa;
SELECT DATABASE ();
#复合约束

create table user1(

id int,
`name` char(10),
`password` char(25),

CONSTRAINT uk_user_name_pwd UNIQUE(`name`,`password`)

);


CREATE TABLE USER(
id INT,
`name` VARCHAR(15),
`password` VARCHAR(25),


CONSTRAINT uk_user_name_pwd UNIQUE (`name`,`password`)

)

select * from user;

INSERT into user
VALUES(1,'tom','abc');

INSERT into user
VALUES(1,'tom111','abc');

desc user;


select * from information_schema.table_constraints
where table_name="user"

ALTER TABLE user
DROP INDEX uk_user_name_pwd ;


CREATE TABLE test(
last_name VARCHAR(15),
salary INT,
email VARCHAR(25)
);

desc test;



CREATE TABLE test5(
id INT,
last_name VARCHAR(15),
salary INT,
email VARCHAR(25),
CONSTRAINT pk_test5_id PRIMARY KEY(id)
);


select * from information_schema.table_constraints
where table_name="test5";


INSERT INTO test5(id,last_name,salary,email)
VALUES(1,'Tom1',4000,'tom@126.com');

SELECT*from test5;

INSERT INTO test5(id,last_name,salary,email)
VALUES(2,'Tom1',4000,'tom@126.com');


CREATE TABLE test8(
id INT,
last_name VARCHAR(15),
salary INT,
email VARCHAR(25),
PRIMARY KEY(last_name,salary)
);

desc test8;

INSERT INTO test8(id,last_name,salary,email)
VALUES(1,'Tom1',4000,'tom@126.com');

SELECT*from test8;

CREATE TABLE test9(
id INT,
last_name VARCHAR(15),
salary INT,
email VARCHAR(25)
);
desc test9;
SELECT*from test9;

ALTER TABLE test9
ADD PRIMARY KEY (id);

ALTER TABLE test9
drop PRIMARY KEY ;