oracle常用函数(4)

ENTRYID,SESSIONID,TERMINAL,ISDBA,LABLE,LANGUAGE,CLIENT_INFO,LANG,VSIZE

ISDBA 查看当前用户是否是DBA如果是则返回true SQL> select userenv('isdba') from dual; USEREN ------ FALSE

SQL> select userenv('isdba') from dual; USEREN ------ TRUE SESSION 返回会话标志

SQL> select userenv('sessionid') from dual; USERENV('SESSIONID') -------------------- 152 ENTRYID 返回会话人口标志

SQL> select userenv('entryid') from dual; USERENV('ENTRYID') ------------------ 0 INSTANCE

返回当前INSTANCE的标志

SQL> select userenv('instance') from dual; USERENV('INSTANCE') ------------------- 1 LANGUAGE 返回当前环境变量

SQL> select userenv('language') from dual; USERENV('LANGUAGE')

---------------------------------------------------- SIMPLIFIED CHINESE_CHINA.ZHS16GBK LANG

返回当前环境的语言的缩写

SQL> select userenv('lang') from dual; USERENV('LANG')

---------------------------------------------------- ZHS TERMINAL

返回用户的终端或机器的标志

SQL> select userenv('terminal') from dual; USERENV('TERMINA ---------------- GAO VSIZE(X)

返回X的大小(字节)数

SQL> select vsize(user),user from dual; VSIZE(USER) USER

----------- ------------------------------ 6 SYSTEM

60.AVG(DISTINCT|ALL)

all表示对所有的值求平均值,distinct只对不同的值求平均值 SQLWKS> create table table3(xm varchar(8),sal number(7,2)); 语句已处理。

SQLWKS> insert into table3 values('gao',1111.11); SQLWKS> insert into table3 values('gao',1111.11); SQLWKS> insert into table3 values('zhu',5555.55);

SQLWKS> commit;

SQL> select avg(distinct sal) from gao.table3; AVG(DISTINCTSAL) ---------------- 3333.33

SQL> select avg(all sal) from gao.table3; AVG(ALLSAL) ----------- 2592.59

61.MAX(DISTINCT|ALL)

求最大值,ALL表示对所有的值求最大值,DISTINCT表示对不同的值求最大值,相同的只取一次

SQL> select max(distinct sal) from scott.emp; MAX(DISTINCTSAL) ---------------- 5000

62.MIN(DISTINCT|ALL)

求最小值,ALL表示对所有的值求最小值,DISTINCT表示对不同的值求最小值,相同的只取一次

SQL> select min(all sal) from gao.table3; MIN(ALLSAL) ----------- 1111.11

63.STDDEV(distinct|all)

求标准差,ALL表示对所有的值求标准差,DISTINCT表示只对不同的值求标准差 SQL> select stddev(sal) from scott.emp; STDDEV(SAL)

----------- 1182.5032

SQL> select stddev(distinct sal) from scott.emp; STDDEV(DISTINCTSAL) ------------------- 1229.951

64.VARIANCE(DISTINCT|ALL) 求协方差

SQL> select variance(sal) from scott.emp; VARIANCE(SAL) ------------- 1398313.9

65.GROUP BY

主要用来对一组数进行统计

SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno; DEPTNO COUNT(*) SUM(SAL) --------- --------- ---------

10 3 8750 20 5 10875 30 6 9400

66.HAVING

对分组统计再加限制条件

SQL> select deptno,count(*),sum(sal) from scott.emp group by deptno having count(*)>=5; DEPTNO COUNT(*) SUM(SAL) --------- --------- ---------

20 5 10875 30 6 9400

SQL> select deptno,count(*),sum(sal) from scott.emp having count(*)>=5 group by deptno ; DEPTNO COUNT(*) SUM(SAL)

--------- --------- ---------

20 5 10875 30 6 9400

67.ORDER BY

用于对查询到的结果进行排序输出

SQL> select deptno,ename,sal from scott.emp order by deptno,sal desc; DEPTNO ENAME SAL --------- ---------- ---------

10 KING 5000 10 CLARK 2450 10 MILLER 1300 20 SCOTT 3000 20 FORD 3000 20 JONES 2975 20 ADAMS 1100 20 SMITH 800 30 BLAKE 2850 30 ALLEN 1600 30 TURNER 1500 30 WARD 1250 30 MARTIN 1250 30 JAMES 950

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