知识点
查询语句得到的是一个结果集,增删改得到的是影响的行数
删除一行数据,主键 id 不会自动变化
基本操作
查询:
select id, name from users;
select ` id` , ` name` from ` users` ;
select * from users;
select 'foo' from users;
新增:
insert into users values ( null , 'CEO' , '张三' , 12 ) ;
insert into users value ( null , 'CEO' , '张三' , 12 ) ;
insert into users ( title, name, age) values ( 'CEO' , '张三' , 12 ) ;
删除:
delete from users where title= 'ufo' and id> 1
delete from users where id in ( 1 , 2 , 3 , 4 )
修改:
update users set title = 'CEO' , name = '张三' where id = 1
常见查询函数
select count ( id) from users;
select max ( id) from users;
select * from users limit 2 ;
select * from users limit 4 , 2 ;
php操作
$connection = mysqli_connet ( '127.0.0.1' , 'root' , '1234' , 'user' )
mysqli_set_charset ( $connection , 'utf8' ) ;
if ( ! $connection ) {
exit ( '<h1>连接数据库失败</h1>' ) ;
}
$query = mysqli_query ( $connection , 'select * from users' )
while ( $row = mysqli_fetch_assoc ( $query ) ) {
var_dump ( $row ) ;
}
mysqli_free_result ( $query ) ;
mysqli_close ( $connection ) ;
$query = mysqli_query ( $connection , 'delete from users where id = 5;' ) ;
if ( ! $query ) {
exit ( '<h1>查询失败</h1>' ) ;
}
$rows = mysqli_affected_rows ( $connection ) ;