Oracle数据库常用SQL语句查询

查询第一条记录

where语句后面跟上 and rownum=1

2.日期所相差分钟数

ceil((LOGOUT_TIME - LOGIN_TIME) * 24 * 60)

3.group by分组后，取得分组前的每一组的第一条记录

---获取15届学生第一次登录wifi的最早时间

select * from (

select wifilogin.*,row_number() over(partition by USER_ID order by rownum)cn from T_SAM_YHDLXX

) wifilogin

)where cn='1'

4.查询某用户被赋予的表权限

SELECT * FROM user_tab_privs_made where grantee='USR_GIS'

5. 按名称查询视图

select view_name from user_views where view_name like 'V%'

6. 查询数据表所占用的空间

select OWNER, t.segment_name, t.segment_type, sum(t.bytes / 1024 / 1024) mmm
from dba_segments t
where t.owner = '用户名'
and t.segment_type='TABLE'
--and t.segment_name='表名'
group by OWNER, t.segment_name, t.segment_type
order by mmm desc;
7，查询库中所含的表、列、数据行（

https://www.cnblogs.com/JohanChan/p/11718183.html）

 SELECT COUNT(*) TABLES, table_schema FROM information_schema.TABLES   WHERE table_schema = 'szdb'

 SELECT COUNT(column_name) FROM information_schema.COLUMNS WHERE TABLE_SCHEMA = 'szdb';

use information_schema;

SELECT sum(table_rows) from tables where TABLE_SCHEMA = 'szdb' order by table_rows desc;

8.日期格式转换

substr(xn,1,4)>=(to_char(sysdate,'yyyy')-4)

 查看所有表空间的数据使用情况
SELECT Upper(F.TABLESPACE_NAME)         "表空间名",
       D.TOT_GROOTTE_MB                 "表空间大小(M)",
       D.TOT_GROOTTE_MB - F.TOTAL_BYTES "已使用空间(M)",
       To_char(Round(( D.TOT_GROOTTE_MB - F.TOTAL_BYTES ) / D.TOT_GROOTTE_MB * 100, 2), '990.99')
       || '%'                           "使用比",
       F.TOTAL_BYTES                    "空闲空间(M)",
       F.MAX_BYTES                      "最大块(M)"
FROM   (SELECT TABLESPACE_NAME,
               Round(Sum(BYTES) / ( 1024 * 1024 ), 2) TOTAL_BYTES,
               Round(Max(BYTES) / ( 1024 * 1024 ), 2) MAX_BYTES
        FROM   SYS.DBA_FREE_SPACE
        GROUP  BY TABLESPACE_NAME) F,
       (SELECT DD.TABLESPACE_NAME,
               Round(Sum(DD.BYTES) / ( 1024 * 1024 ), 2) TOT_GROOTTE_MB
        FROM   SYS.DBA_DATA_FILES DD
        GROUP  BY DD.TABLESPACE_NAME) D
WHERE  D.TABLESPACE_NAME = F.TABLESPACE_NAME
ORDER  BY 1

10. 查看表空间的名字和所属文件
select tablespace_name, file_id, file_name,
round(bytes/(1024*1024),0) total_space
from dba_data_files
order by tablespace_name;

11.手动增加数据文件尺寸
ALTER DATABASE DATAFILE '/oracle/oradata/GAME.dbf'
RESIZE 4000M;

12,筛选时间范围

where to_date(substr(AUTHORIZE_DATE,1,10),'yyyy-mm-dd') >=to_date('2016-09-30','yyyy-mm-dd')

and to_date(substr(AUTHORIZE_DATE,1,10),'yyyy-mm-dd') <=to_date('2017-08-31','yyyy-mm-dd')

where opertime >to_date('2021-04-14 07:00','yyyy-mm-dd HH24:Mi') order by OPERTIME desc

注意是HH24：Mi 不是hh:mm否则会报ORA-01810: 格式代码出现两次的错误。

13 查看所有表空间对应的数据文件：

select sum(bytes)/1024/1024/1024||'GB' from DBA_DATA_FILES;

Oracle数据库常用SQL语句查询

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