一、常见操作 1、解锁 alter user scott account unlock; 2、改密码 alter user scott identified by tiger; 3、查看存在的用户 select * from dba_users; 4、当前用户下存在的表 select * from user_tables; 二、help index(sql *plus命令列表) 有关某个主题的帮助, 请键入 help 常用的/、list、@(start)、@@、CONNECT、define、describe、disconnect、edit、execute、exit、list、set、show、spool、sqlplus 三、set命令 关闭sql *plus设置的命令不再被保留。 解决方法： sql *plus启动会读两个文件($oracle_home/sqlplus/admin目录下)：glogin.sql、login.sql（优先级高） 所以可以创建自己的login.sql文件，常见的设置如下： –_editor是预定义变量制订了当你使用edit命令的时候启动哪个编辑器、edit命令调用编辑器 define _editor = E:\Notepad++\notepad++.exe set linesize 3000 set pagesize 1000 set timing on set null –每行左边的提示符 set sqlprompt ‘&_user@&_connect_identifier> ‘ 四、执行命令 sql语句和sql *plus命令可以在sql *plus中执行 sql语句：分号(命令末尾或空行)或正斜线（必须空行） sql *plus命令：直接敲回车，如describe和connect 五、5个核心的sql语句 ***写在前面：建议写表名时把用户名也写上去，比如from emp，即使你是已scott登录的，也写成from scott.emp，养成好的习惯。 1、select语句 from子句（表、驶入、物化视图、分区、子分区、子查询）：处理联结语句的顺序：交叉联结（笛卡尔乘积）、内联结、外联结； where子句(比较结果true、false、null(当作false对待))； group by子句（select 列表中的任何非聚合字段都必须包括在group by表达式中）； having子句； order by子句（结果集很大时、排序是个开销很大的步骤）。 示例： SELECT c.customer_id, COUNT(o.order_id) AS orders_ct FROM oe.customers c JOIN oe.orders o ON c.customer_id = o.customer_id WHERE c.gender = ‘F’ GROUP BY c.customer_id HAVING COUNT(O.ORDER_ID) > 4 ORDER BY orders_ct, c.customer_id; select列表（标量子查询在结果集中的每一行结果产生时都要执行一遍，代价大！） SELECT c.customer_id, c.cust_first_name ||’ ‘ ||c.cust_last_name, ( SELECT e.last_name FROM hr.employees e WHERE e.employee_id = c.account_mgr_id ) acct_mgr FROM oe.customers c; 2、insert语句 单表插入：子查询插入非常灵活 INSERT INTO scott.bonus ( ename, job, sal ) SELECT ename, job, sal * .10 FROM scott.emp; 多表插入： create table small_customers (customer_id number, sum_orders number) ; create table medium_customers (customer_id number, sum_orders number) ; create table large_customers (customer_id number, SUM_ORDERS NUMBER) ; INSERT ALL WHEN sum_orders < 10000 THEN INTO small_customers WHEN sum_orders >= 10000 AND sum_orders < 100000 THEN INTO medium_customers ELSE INTO large_customers SELECT customer_id, SUM(order_total) sum_orders FROM oe.orders GROUP BY customer_id ; 3、update语句 表达式更新一个单列： UPDATE employees SET salary = salary * 1.10 WHERE department_id = 90 ; 子查询更新一个单列： UPDATE hr.employees employees SET salary = ( SELECT employees2.salary FROM employees2 WHERE employees2.employee_id = employees.employee_id AND EMPLOYEES.SALARY != EMPLOYEES2.SALARY ) WHERE department_id = 90 ; 在where子句中使用子查询确定要更新的数据行来更新单列： UPDATE hr.employees SET salary = salary * 1.10 WHERE department_id IN ( SELECT department_id FROM DEPARTMENTS WHERE department_name = ‘Executive’ ) ; 使用select语句定义表及列的值来更新表： UPDATE ( SELECT e1.salary, e2.salary new_sal FROM hr.employees e1, employees2 e2 WHERE e1.employee_id = e2.employee_id AND E1.DEPARTMENT_ID = 90 ) SET salary = new_sal; 子查询更新多列： UPDATE hr.employees employees SET ( salary, commission_pct ) = ( SELECT employees2.salary, .10 comm_pct FROM employees2 WHERE employees2.employee_id = employees.employee_id AND EMPLOYEES.SALARY != EMPLOYEES2.SALARY ) WHERE department_id = 90 ; 4、delete语句 使用where子句中的筛选条件来从指定表中删除行： DELETE FROM employees2 WHERE department_id = 90; 使用from 子句中的子查询来删除行： DELETE FROM ( SELECT * FROM employees2 WHERE department_id = 90 ); 使用where子句中的子查询来从指定表中删除行： DELETE FROM employees2 WHERE department_id IN ( SELECT department_id FROM hr.departments WHERE department_name = ‘Executive’ ); 5、merge语句（Oracle9i新增的语法,用来合并UPDATE、INSERT、delete语句，常用在数据仓库中移动大量的数据） CREATE TABLE dept60_bonuses ( employee_id NUMBER ,bonus_amt NUMBER ); merge INTO dept60_bonuses b USING ( SELECT employee_id, salary, department_id FROM hr.employees WHERE department_id = 60 ) e ON (b.employee_id = e.employee_id) WHEN matched THEN UPDATE SET b.bonus_amt = e.salary * 0.2 WHERE b.bonus_amt = 0 DELETE WHERE (e.salary > 7500) WHEN NOT matched THEN INSERT ( b.employee_id, b.bonus_amt ) VALUES ( E.EMPLOYEE_ID, E.SALARY * 0.1 ) WHERE (e.salary < 7500);