Oracle高级查询,事物,过程及函数

一 数值函数

数值 abs,ceil,floor,round,trunc字符串 instr,substr

SQL>SELECT 'ABS':'|| ABS(-12.3) FROM DUAL;

运行结果:

ABS:12.3

SQL>SELECT 'CEIL'||CELI(5.3) FROM DUAL;
SQL>SELECT 'CEIL'||CELI(-5.3) FROM DUAL;
SQL>SELECT 'CEIL'||CELI(5) FROM DUAL;

运行结果:
CEIL:6
CEIL:-5
CEIL:5

SQL>SELECT 'FIOOR'||FIOOR(5.3) FROM DUAL;
SQL>SELECT 'FIOOR'||FIOOR(-5.3) FROM DUAL;
SQL>SELECT 'FIOOR'||FIOOR(5) FROM DUAL;

运行结果:

CEIL:5
CEIL:-6
CEIL:5

 

SQL>SELECT 'ROUND'||ROUND(1346.1233,0) FROM DUAL;
SQL>SELECT 'ROUND'||ROUND(1546.1233,-3) FROM DUAL;
SQL>SELECT 'ROUND'||ROUND(1346.1233,3) FROM DUAL;

运行结果:

ROUND:1346
ROUND:2000
ROUND:1346.1

 

SQL>SELECT 'TRUNC'||TRUNC(1346.1233,0) FROM DUAL;
SQL>SELECT 'TRUNC'||TRUNC(1546.1233,-3) FROM DUAL;
SQL>SELECT 'TRUNC'||TRUNC(1346.1233,2) FROM DUAL;

运行结果:

ROUND:1346
ROUND:1000
ROUND:1346.12

字符函数
字符型LOWER(CHAR)转化为小写
UPPER(CHAR)转化为大写
LENGTH(CHAR)返回字符串长度
LTRIM(CHAR[,SET])去掉char中的set
REPLACE替换
LTRIM 去掉左空格
RTRIM 去掉右空格
SUBSTR截取
转换
to_number() to_date() to_char() NVL() NVL2(),
SQL>SELECT 'to_number':'|| to_number('2000.22','999d9999') FROM DUAL;
运行结果:
to_number:2000.22
SQL>SELECT 'to_date':'|| to_date(sysdate,'dd-mm-yy') FROM DUAL;
运行结果:
to_date:13-12-13
SQL>SELECT 'to_char':'|| o_char('12-13-13','mm-dd-yy') FROM DUAL;
运行结果:
to_char:2013-12-13
SQL>SELECT 'NVL':'|| NVL(COMM,0) FROM SCOTT,EMP WHERE EMPNO=7369;
运行结果:
to_char:0
SQL>SELECT 'NVL2':'|| NVL2(COMM,0,1) FROM SCOTT,EMP WHERE EMPNO=7369;
运行结果:
to_char:1

时间函数
add_months months_between
分组函数
min max avg sum count
分析函数
row_number() over(order by 列) ,
多表查询
操作符 UNION(补) UNION ALL(并) INTERSECT(交) MINUS(差)

二 内,外连接 子查询 自连接 联合查询
内连接
select dept.deptno,dname,ename from scott.dept,scott.emp where dept.deptno=emp.deptno;
自连接
select manager.ename from scott.emp manager scott.emp worker where manager.deptno=worker.mgr and worker.ename='SMITH';
内连接/外链接
select table1.column,table2.column from table1[inner|left|right|full]join table2 on table1.column1=table2.column2;

事务
(ACID) saveppoint a commit（提交）、rollback（滚回去）:
只要涉及到数据的增、删、改就会产生事物，事物要么执行提交，要么全部失败。
执行commit之后会释放在会话中所有的行和表锁。一旦执行就不能用rollback恢复。
自动提交事物：执行DDL（create table ,alter table ,drop table ）、DCL（grant ,revoke）和退出SQL*plus时。

　　事物的ACID属性:原子性,一致性,隔离性,持久性