Oracle SQL语句大全

作者：[网上资料 ]

ORDER BY 排序ASC 升序(默认)DESC 降序select * from s_emp order by dept_id , salary desc部门号升序，工资降序关键字distinct也会触发排序操作。select * from employee order by 1; //按第一字段排序NULL被认为无穷大。order by 可以跟别名。select table_name from user_tables where table_name='S_EMP'; 查某个具体表名时，表名的字符串必须要为大写或者采用 upper(table_name)select * from user_talbes where table_name like ‘s\_%’ escape ‘\’;使用转义字符对关键字进行转义。concat 连接字符串 select concat(first_name , last_name) from s_emp;等效于||substr 求子串 select substr('tarenasd0603' ,1,6) from dual; (取前六个字符) select substr('tarenasd0603',-2) from dual; (取后两个字符)length 求字符长度select length('zhonghua') from dual;from dual的意思虚表（dual）是oracle提供的最小的工作表，它仅包含一行一列。对于虚表（dual）来说，其中的列往往是不相关的或无关紧要的。     如：查询当前的系统日期     SQL>   select   sysdate   from   dual;         SYSDATE     -------------------     2004/04/28   08:49:41round 函数(四舍五入) select round(45.935, 2) from dual; 不带参数时默认为0位小数trunc 函数(截取，不管后面的数字) select trunc(45.995, 1) from dual;组函数group by 分组子句 对分组后的子句进行过滤还可以用having 条件 对分组后的条件进行过滤 where 是对记录进行过滤有佣金人数的百分比select count( commission_pct )count(*) from s_emp;select count(dept_id) from s_emp;select count(distinct dept_id) from s_emp;//区分相同的dept_id求各个部门的平均工资：group by 子句也会触发排序select dept_id , avg(salary) aa from s_emp group by dept_id order by aa ; //对平均工资排序select dept_id , avg(salary) aa from s_emp group by dept_id;哪些部门的平均工资比2000高:select dept_id, avg(salary) aa from s_emp group by (dept_id) having avg(salary)>2000;除了42部门以外的部门的平均工资:select dept_id , avg(salary) from s_emp group by (dept_id ) having dept_id!=42;select dept_id , avg(salary) from s_emp where dept_id!=42 group by (dept_id ) ;(此种sql效率要高，先过滤) 再计算）where 单行函数。having 组函数。每个员工所在的部门和部门所在的地区select first_name , s_dept.name, s_region.name from s_emp, s_dept, s_region wheres_emp.dept_id=s_dept.id and s_dept.region_id=s_region.id;等价于select first_name,d.name,r.namefrom s_emp e,s_dept d,s_region rwhere e.dept_id=d.id and d.region_id=r.id; |