隨機(jī)獲取oracle數(shù)據(jù)庫(kù)數(shù)據(jù)量

  // 從全表數(shù)據(jù)隨機(jī)抽取10%，獲取前10條數(shù)據(jù)
  select * from 表名 sample(10) where rownum > 10;

查看oracle數(shù)據(jù)庫(kù)的所有表

  select * from user_tables

查看某個(gè)表的字段和類(lèi)型，默認(rèn)值，字段注釋

 select 
   a.column_name,
   a.data_type,a.data_length,a.nullable,
   a.data_default,
   b.comments 
 from 
    user_tab_columns a,
    user_col_comments b 
 where 
    a.table_name = b.table_name 
 and 
    a.column_name = b.column_name 
 and 
    a.table_name = '表名'(表名要大寫(xiě))

查看某個(gè)表的主鍵

 select
   b.column_name
 from
   user_constraints a,
   user_cons_columns b
 where
   a.constraint_name=b.constraint_name 
 and 
   a.constraint_type='P'
 and 
    b.table_name='表名'(表名要大寫(xiě))

查看某個(gè)表的外鍵

 select * from user_constraints where constraint_type='R' and table_name = '表名'(表名要大寫(xiě))

查看某個(gè)表的前幾行數(shù)據(jù)，在oracle沒(méi)有l(wèi)imit操作

 select * from 表名 where rownum < 行數(shù);