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));"," ALTER TABLE commercials CHANGE (description CHAR2(2000));"," ALTER TABLE commercials CHANGE (description VARCHAR2 (2000));"," ALTER TABLE commercials MODIFY (description VARCHAR2 (2000));"," You cannot increase the size of a column if the table has rows."]
起重钢绳虽无断丝，但每根钢丝磨损或腐蚀超过其直径多少应报费（）。 ["50%","40%","30%"]
You work as a database administrator for Supportcenter.cn. You are using Recovery Manager （RMAN） to perform backups in your databases. Which four backup operations can be performed using RMAN？（） ["A backup of the target database when it is mounted","A backup of online redo log files when the database is open","A backup of only used data blocks in the file beingbeingbackup up","A backup of online， read\/write data files when the database is open","A backup of only those data blocks that have changed since a previous backup","A backup of online， read\/write data files when the database is in the NOMOUNT state."]
小企业如何综合利用各种法律，以达到最佳经营效益？
男性，30岁，因车祸致双下肢挤压伤住院，第2天自感头痛头晕、呼吸费力，尿量每小时少于17ml，应考虑其危险是（） ["ARDS","MODS","ARF","休克","心功能衰竭"]
如何建立小企业的社会道德？
