增删改查(crud)
(一)增
<1>插入完整行
insert into values(001,'姓名',18,'男');
<2>根据列插入数据
insert into student(id,name,age,gender)
values(001,'姓名',18,'男');
<3>多行插入数据
insert into student(id,name,age,gender)
values(001,'姓名',18,'男');
values(002,'姓名',19,'男');
values(002,'姓名',18,'女');
<4>讲一个表里的子列插入到另一个表里
insert into newStudent(列名,列名) select 列名 from student;
(二)删
<１>删除一行
delete from student where userid=10010;
<2>删除表中所有行
delete from student;
(三)改
<1>把字段age的值为20
updata student SET age='20' where id=10010;
<2>改多个列
updata studata age='20' name='姓名' where id=10010;
(四)查
<1>查询单个列
select name from student;
<2>查询多个列
select age,name,phonenum from student;
<3>查询所有列
select * from student;
<4>查询不同的列
SELECT DISTINCT name FROM student;
<5>查询完全限定的表名
SELECT student.name,student.age FROM student;
数据的查询WHERE（过滤）
<1> = 等于
select name from customers where name='李逵';
<2> <> 不等于
select name from customers where name<>'李逵';
<3> != 不等于
select name from customers where name!='李逵';
<4> < 小于 (一般情况下后面会跟数字)
select name from customers where name<'李逵';
select * from customers where userid<10014;
<5> <= 小于等于
select * from customers where userid<=10014;
<6> ＞ 大于
select * from customers where userid>10014;
<7> ＞= 大于等于
select * from customers where userid>=10014;
<8>空值检查(IS NULL)
SELECT name FROM students WHERE age IS NULL;
<9>AND操作符
SELECT name,age FROM student WHERE name='姓名' AND age =18;
<10>OR 操作符
SELECT name FROM studentb WHERE name='姓名' OR age=18;
<11>IN操作符
SELECT name FROM studentb WHERE id IN(001,003);
<12>NOT 操作符
SELECT name FROM studentb WHERE id NOT IN(001,003);
