Oracle 删除表中记录 如何释放表及表空间大小

转载自：http://blog.csdn.net/xixi_666/article/details/48179865

1.查看一个表所占的空间大小：
SELECT bytes/1024/1024 ||'MB' TABLE_SIZE ,u.* FROM USER_SEGMENTS U WHERE U.SEGMENT_NAME='JK_TEST';
2.查看一个表空间所占的实际大小：
SELECT SUM(BYTES) / 1024 / 1024 ||'MB' FROM USER_SEGMENTS U  WHERE
TABLESPACE_NAME = 'DATA01';
3.查看一个表空间对应的数据文件：
SELECT * FROM DBA_DATA_FILES D WHERE D.TABLESPACE_NAME = 'DATA01';
4.查看表空间的使用情况：
SELECT A.TABLESPACE_NAME,      
       FILENUM,   
       TOTAL
"TOTAL (MB)",  
       F.FREE
"FREE (MB)",
       TO_CHAR(ROUND(FREE
* 100 / TOTAL, 2), '990.00') "FREE%", 
       TO_CHAR(ROUND((TOTAL
- FREE) * 100 / TOTAL, 2), '990.00') "USED%",    
       ROUND(MAXSIZES,
2) "MAX (MB)"
  FROM
(SELECT TABLESPACE_NAME,          
               COUNT(FILE_ID)
FILENUM,        
               SUM(BYTES
/ (1024 * 1024)) TOTAL,          
               SUM(MAXBYTES)
/ 1024 / 1024 MAXSIZES      
          FROM
DBA_DATA_FILES       
         GROUP
BY TABLESPACE_NAME) A,     
       (SELECT
TABLESPACE_NAME, ROUND(SUM(BYTES / (1024 * 1024))) FREE     
          FROM
DBA_FREE_SPACE      
         GROUP
BY TABLESPACE_NAME) F
 WHERE
A.TABLESPACE_NAME = F.TABLESPACE_NAME
5.查看数据文件的实际使用情况：
SELECT CEIL(MAX_BLOCK * BLOCK_SIZE / 1024)
  FROM
(SELECT MAX(BLOCK_ID) MAX_BLOCK
          FROM
DBA_EXTENTS
         WHERE
FILE_ID IN (SELECT FILE_ID
                             FROM
DBA_DATA_FILES D