2.1 where
作用：限制行的查询
例2.1.1
SQL> select dname from scott.dept
where deptno = 10;
2.2 Between
Between
100 and 103 :包含100和103
例2.2.1
SQL>select DNAME from scott.dept
where deptno between 10 and 30;
例2.3.1
SQL>select * from scott.dept;
DEPTNO DNAME LOC
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
41 A%%%%%%% A
42 A%_%%%%% B
SQL>select dname from scott.dept
where deptno in (40,42);
DNAME
--------------
OPERATIONS
A%_%%%%%
2.4 like
2.4.1 作用：模糊查找，搜索条件可以包含文字字符或数字
1）%表示零或多个字符
2）_表示一个字符
例2.4.1
SQL>select dname from scott.dept
where deptno like '1%';
2.4.2 单引号转义符
Escapez:转义%与_匹配字符本来的含义
方法一：SQL> select ename||q'['s sal is ]'||sal info from scott.emp;
方法二：
SQL> select ename||'''s sal is '||sal from
scott.emp;
例2.4.2
SQL> select ename||'''s sal is '||sal from scott.emp;
ENAME||'''SSALIS'||SAL
------------------------------------------------------------
SMITH's sal is 800
ALLEN's sal is 1600
WARD's sal is 1250
JONES's sal is 2975
MARTIN's sal is 1250
BLAKE's sal is 2850
CLARK's sal is 2450
SCOTT's sal is 3000
SQL> select * from scott.dept;
DEPTNO DNAME LOC
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
例2.4.3
SQL> insert into
scott.dept values (41,'A%%%%%%%','A');
1 row
created.
SQL> select * from scott.dept;
DEPTNO DNAME LOC
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
41 A%%%%%%% A
例2.4.4
SQL> insert into
scott.dept values (42,'A%_%%%%%','B');
1 row
created.
SQL>select * from scott.dept;
DEPTNO DNAME LOC
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
41 A%%%%%%% A
42 A%_%%%%% B
6 rows
selected.
2.4.3 ~
转义符:~的下一个字符如果是%，这个百分号是真实的百分号，没有特殊的含义
例 2.4.5查找A%_开头的
SQL>select * from scott.dept where dname like 'A~%~_%' escape '~';
DEPTNO DNAME LOC
42 A%_%%%%% B
2.5 OR
例2.5.1
SQL>select loc from scott.dept
where deptno >= 10
or dname like 'A%';
2.6 NOT IN
例2.6.1
SQL>select dname from scott.dept
where deptno not in (10,40);
DNAME
--------------
RESEARCH
SALES
A%%%%%%%
A%_%%%%%
2.7 || 连接运算符
SQL> select * from scott.dept;
DEPTNO DNAME LOC
----------
-------------- -------------
10 ACCOUNTING NEW YORK
20 RESEARCH DALLAS
30 SALES CHICAGO
40 OPERATIONS BOSTON
41 A%%%%%%% A
42 A%_%%%%% B
SQL>select
dname ||' is '||deptno
as "name" from scott.dept;
name
----------------------------------------------------------
ACCOUNTING is 10
RESEARCH is 20
SALES is 30
OPERATIONS is 40
A%%%%%%% is 41
A%_%%%%% is 42
2.8 DISTINCT去除重复的行
用法：select distinct 列名 from 表名
例2.8.1
SQL>select id from student1;
ID
----------
1
2
3
4
5
6
7
8
9
9
10 rows
selected.
SQL>select distinct id from student1;
ID
----------
1
6
2
4
5
8
3
7
9
9 rows
selected.
2.9 在sqlplus 环境里执行操作系统命令
用法：
！clear
host 命令
例2.9.1
SQL>!clear
SQL>host echo hehe
hehe
例2.9.2
SQL>host pwd
/home/oracle/Desktop
例2.9.3
2.10 and
例2.10.1
2.11 or
2.12 规则优先
2.13 Order by排序
特点：放在select 语句末尾，默认升序（asc）,降序是desc
2.13.1 降序
2.13.2用列别名排序
2.13.3 用列所在数字位排序
2.13.4 多列排序
2.14 替代变量
特点：临时变量用&，调用替代变量用&&，变量中的字符和日期要用单引号引起来。
用法：select 列名 from
表名 where 列名 = &新列名；
用途：
where 子句
order 子句
列表达式
表名
整个语句
例2.14.1
SQL>select id,name
2 fromstudent
3 where id = &stid
4 ;
Enter
value for stid: 2
old 3: where id = &stid
new 3: where id = 2
ID NAME
----------
--------------------
2
xixi
2.15 define创建和分配一个值到一个变量
undefine取消已定义的变量
例2.15.1
2.16 set verify on|off 变量替换的过程新旧值是否显示
例2.16.1
2.17创建用户
命令格式：create user c##创建的用户名 identified by oracle
SQL>create user c##xigua identified by oracle;
User
created.
2.18 IS(NOT) NULL空值判断
用法：select 条件 f rom 表名 where 列名 is(is
not) null;
例2.18.1
SQL>select * from student
2 where name is not null;
ID NAME SEX AGE COURSE SCORE
1 LISA girl 21 math 80
2 xixi girl 22 english 90
3 Kris Wu boy 20 langauage 88
4 jen girl 25 history 70
5 hz boy 22 computer 60
6 xfy girl 21 computer 99
7 yy boy 22 math 54
8 lanxi girl 21 english 60
9 hony boy 22 history 56
9 rows
selected.