编写并执行ALTER TABLE语句来删除该列: 一旦确认没有其他依赖或已经处理了所有依赖,你可以使用ALTER TABLE语句来删除列。以下是删除employees表中middle_name列的SQL语句: sql ALTER TABLE employees DROP COLUMN middle_name; 验证列是否已成功从表中删除: 你可以通过查询表的结构来验证列是否已被成功删除。这可以通...
(b) alter table set unused column in oracle DROP COLUMN using DROP COLUMN Here in this wedrop the column from table using below command. ALTER TABLE table_name DROP COLUMN col_name; This statement takes exclusive lock on the table and if the table is big, it will take time to execute ...
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_...
经过进一步研究发现数据块等待的对象是 I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST,会话正在更新AWR报告相关视图的索引信息,所以比较慢。 2、Oracle bug,可能性很低 Bug 6781367 - ALTER TABLE ADD COLUMN or mass UPDATE can be slow in ASSM (文档 ID 6781367.8) 解决方案: 清理那个表和索引,收集统计信息 analyze t...
Oracle DROP COLUMN clause example The following statement removes theemailandphonecolumns from thesupplierstable: ALTERTABLEsuppliersDROP( email, phone );Code language:SQL (Structured Query Language)(sql) In this tutorial, you have learned how to use the Oracle drop column statement to delete one ...
在OceanBase 数据库 MySQL 模式以及 Oracle 模式中直接删除含主键的列可以通过先删除主键、再删除对应的列的方式,来实现删除主键列的目的。涉及的语句如下。 ALTER TABLE table_a DROP PRIMARY KEY; ALTER TABLE table_a DROP COLUMN ID; OceanBase 数据库 MySQL 模式下删除主键的操作。 创建表。 obclient [mys...
We are having performance issues with the following drop column statement in production. alter table tbl_rt_request_event drop column message_clr;
Oracle issued the following error: This is because the primary key of thebrandstable is currently referenced by thebrand_idcolumn in thecarstable. The following statement returns all foreign key constraints of thecarstable: SELECTa.table_name, a.column_name, a.constraint_name, c.owner, c.r_...
Oraclesql文章分类代码人生 我 们要删除表中不用的字段,如果直接drop column,对于大表,进行DDL操作的时间会比较长,会严重阻塞DML语句,导致应用服务器crash,通常的做法是先set unused column column_name 或者 set unused column_name,column_name...,然后再利用停机时间做alter table table_name drop unused columns...
ORA-39726: unsupported add/drop column operation on compressed tables 解决方法: 1. 如果是空表,删除,重建即可 2. compress for all operations; SQL> alter table test_compress compress for all operations; Table altered. SQL> alter table test_compress drop column object_name; ...