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。这可以通过DESC命令或查询ALL
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...
My SQL / Oracle (prior version 10G): ALTERTABLEtable_name MODIFYCOLUMNcolumn_name datatype; Oracle 10G and later: ALTERTABLEtable_name MODIFYcolumn_name datatype; SQL ALTER TABLE Example Look at the "Persons" table: IDLastNameFirstNameAddressCity ...
If you are not the owner of the table, you need the DROP ANY TABLE privilege in order to use the drop_table_partition or truncate_table_partition clause. You must also have space quota in the tablespace in which space is to be acquired in order to use the add_table_partition, modify_...
ALTER TABLE t2 ADD INDEX (d), ADD UNIQUE (a); To remove column c: ALTER TABLE t2 DROP COLUMN c; To add a new AUTO_INCREMENT integer column named c: ALTER TABLE t2 ADD c INT UNSIGNED NOT NULL AUTO_INCREMENT, ADD PRIMARY KEY (c); ...
Oracle中drop_column的几种方式和风险 墨墨导读:你是否足够了解在生产环境上执行drop column操作或者类似的DDL操作有多危险? 生产环境的一张大表上执行了一个drop column,导致业务停止运行几个小时,这样的事情发生任何一位DBA身上,都会有一种深秋的悲凉。你是否足够了解在生产环境上执行drop column操作或者类似的DDL...
在表table_name中增加了列column,类型为INT 2.在数据表中删除列 ALTER TABLEtable_nameDROPcolumn 在表table_name中删除了列column 3.在数据表中修改列的类型 ALTER TABLEtable_nameMODIFYcolumnVARCHER(20) 在表table_name中修改列column的类型为VARCHER(20),如果精度不一致,则需保证列为空。如果精度一致,则需满...
ALTER TABLE t2 ADD INDEX (d), ADD UNIQUE (a); To remove column c: ALTER TABLE t2 DROP COLUMN c; To add a new AUTO_INCREMENT integer column named c: ALTER TABLE t2 ADD c INT UNSIGNED NOT NULL AUTO_INCREMENT, ADD PRIMARY KEY (c); ...
Here, the SQL command changes the data type of theagecolumn toVARCHARin theCustomerstable. Note:This command is not supported by SQLite. Drop Column in a Table We can also drop (remove) columns in a table using theALTER TABLEcommand with theDROPclause. For example, ...
alter table t add (sex varchar2(1)); 发现执行该语句时是以NOWAIT方式对表添加了一个ROW EXCLUSIVE模式锁: LOCK TABLE "T" IN ROW EXCLUSIVE MODE NOWAIT 我们看下Oracle的官方解释: ROW SHARE ROW SHARE permits concurrent access to the locked table but prohibits users from locking the entire table ...