文件名称：丢弃一个列-SQL语言基础
文件大小：5.26MB
文件格式：PPT
更新时间：2024-05-15 13:25:09
SQL 基础
丢弃一个列 * 使用 DROP COLUMN来丢弃一个表中将来不使用的列. SQL> ALTER TABLE dept30 2 DROP COLUMN job ; Table altered. * Dropping a Column You can drop a column from a table by using the ALTER TABLE statement with the DROP COLUMN clause. This is a feature available from Oracle8i onward. Guidelines The column may or may not contain data. Only one column can be dropped at a time. The table must have at least one column remaining in it after it is altered. Once a column is dropped, it cannot be recovered.