You need to change the definition of an existing table. The COMMERCIALS table needs its DESCRIPTION column changed to hold varying length characters up to 2000 bytes. The column can currently hold 1000 bytes per value. The table contains 20000 rows. Which statement is valid?()
ALTER TABLE commercials MODIFY (description CHAR2(2000));
B. ALTER TABLE commercials CHANGE (description CHAR2(2000));
C. ALTER TABLE commercials CHANGE (description VARCHAR2 (2000));
D. ALTER TABLE commercials MODIFY (description VARCHAR2 (2000));
E. You cannot increase the size of a column if the table has rows.
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A. 正确
B. 错误
下列溶解能溶解PP的为()。
A. 芳烃
B. 苯酚
C. EG
D. 丙酮
项目信息管理的目的是()。
A. 协调各建设单位的关系
B. 为项目建设的增值服务
C. 确保施工进度
D. 有效地进行文件档案管理