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_TAB_COLUMNS视图来实现。 sql DESC employees; 或者: sql SELECT COLUMN_NAME FROM ALL_TAB_COLUMNS WHERE TABLE_NAME = 'EMPLOYEES' AND OWNER = ...
DROP UNUSED COLUMNS; 如果要减少累积的撤消日志量,可以使用CHECKPOINT选项,该选项在指定的行数已被处理后强制检查点。 ALTER TABLE table_name DROP UNUSED COLUMNS CHECKPOINT 250; Oracle SET UNUSED COLUMN示例 下面来创建一个名为suppliers的示例表: -- 12c语法 CREATE TABLE suppliers ( supplier_id NUMBER GENER...
We often need to drop the column in the table. There are two ways to drop the column in Oracle (a) alter table drop column in oracle (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 ...
In Oracle, the possibility to drop a column/columns in an existing table can be available only after the origin of oracle 8i. The column/columns in a table can be dropped either logically or physically, but most of the time we use the logic delete. And for this the "ALTER TABLE" ...
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。
Oracle Drop Column Summary: in this tutorial, you will learn how to use the Oracle drop column statements to remove one or more columns from a table. Oracle Drop Column using SET UNUSED COLUMN clause The process of dropping a column from a big table can be time and resource-consuming. ...
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...
DROP TABLE brands; Oracle发出以下错误: ORA-02449: unique/primary keys in table referenced by foreign keys 这是因为brands表的主键当前由cars表中的brand_id列引用。 以下语句返回cars表的所有外键约束: SELECT a.table_name, a.column_name, a.constraint_name, ...
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 table SYS.WRI$_OPTSTAT_HISTGRM_HISTORY compute statistics ; alter index "sys"."I_WRI$_OPTSTAT_H_OBJ#_ICOL#_ST" rebuild...
In MySQL, the syntax for ALTER TABLE Drop Column is, ALTER TABLE "table_name" DROP "column_name"; In Oracle, SQL Server, and Google BigQuery, the syntax for ALTER TABLE Drop Column is, ALTER TABLE "table_name" DROP COLUMN "column_name"; Let...