Oracle Drop Column using SET UNUSED COLUMN clause# The process of dropping a column from a big table can be time and resource-consuming. Therefore, we typically drop the column logically by using theALTER TABLE SET UNUSED COLUMNstatement as follows: ALTERTABLEtable_nameSETUNUSEDCOLUMNcolumn_name;...
场景一:直接drop column 运行业务模拟程序,开始正常插入日志,然后删除大表的字段。 alter table t_test_col drop column vard; 影响范围: drop column操作耗时30多秒; insert 语句在drop column完成之前无法执行,等待事件为enq:TM-contention; select不受影响。 场景二:先set unused然后再drop alter table t_test_...
场景一:直接drop column 运行业务模拟程序,开始正常插入日志,然后删除大表的字段。 altertablet_test_coldropcolumn vard; 1. 影响范围: drop column操作耗时30多秒; insert 语句在drop column完成之前无法执行,等待事件为enq:TM-contention; select不受影响。 场景二:先set unused然后再drop altertablet_test_colset...
alter table 表名 drop column字段名; 示例:在system空间的test表中删除avg字段; alter table system.test drop column avg; 2.5、查看表 2.5.1 查看表的创建语句 按住ctrl键然后用鼠标左键去点击表名2.5.2 查看表的数据 select * from 表名; 示例:查询system空间下test表的全部数据; select * from system....
alter table pyramid.test_alter2 drop column name; 我的跟踪步骤如下: 13:44:18 sys@DSEDI>select * from v$mystat where rownum<2 ; SID STATISTIC# VALUE --- --- --- 166 0 0 13:44:31 sys@DSEDI>alter table pyramid.test_alter2 drop column name; 这个语句卡死 在新的会话查看非空闲...
假设直接使用底版本号EXP/IMP会出现例如以下错误: EXP-00008: ORACLE error %lu encountered ORA-00904: invalid column name 这已经是一个发布的BUG,须要等到Oracle10.0才干解决,BUG号为2261,你能够到METALINK上去查看有关此BUG的具体信息。 BUG归BUG,我们的工作还是要做,在没有Oracle的支持之前,我们就自己解决。
SQL> update users set newColumn = PID; SQL> commit; SQL> alter table users drop column PID cascade constraints; SQL> alter table users rename column newColumn to PID; SQL> commit; SQL> desc users; 名称 是否为空? 类型 --- --- --- NAME NOT NULL VARCHAR2(10) AGE NUMBER PID VARCHAR...
For example to drop PIN, CITY columns from emp table. alter table emp drop column (pin, city);Remember you cannot drop the column if the table is having only one column.If the column you want to drop is having primary key constraint on it then you have to give cascade constraint ...
And you (almost always) search for rows where the first column of the PK equals some value.This is common for tables in a master-detail relationship. For example:Orders and order items Invoices and invoice lines Flight itineraries and their flights...
COLUMN column_name HEADING column_heading For example: Sql>select * from dept; DEPTNO DNAME LOC --- --- --- 10 ACCOUNTING NEW YORK sql>col LOC heading location sql>select * from dept; DEPTNO DNAME location --- --- --- 10 ACCOUNTING NEW ...