氮源
Examine the data in the EMPLOYEES table. On the EMPLOYEES table, EMPLOYEE_ID is the primary key. MGR_ID is the ID of managers and refers to the EMPLOYEE_ID. The JOB_ID column is a NOT NULL column. Evaluate this DELETE statement: Why does the DELETE statement fail when you execute it?（） There is no row with dept_id 90 in the EMPLOYEES table.。 You cannot delete the JOB_ID column because it is a NOT NULL column.。 You cannot specify column names in the DELETE clause of the DELETE statement.。 You cannot delete the EMPLOYEE_ID column because it is the primary key of the table.。
A型行为模式
简述创设游戏场地的基本要求。
You have configured OMF in your database. You enabled the ALTER DATABASE ENABLE BLOCK CHANGE TRACKING； statement to enable the block change tracking feature. What information will be written in the change tracking file？（） the system change number。 the locations of the redo log files。 the locations of the datafiles。 the physical location of all the database change。
霍桑实验的主要研究结果（）
