delete from employee语句的作用是( )
A.删除当前数据库中整个employee表,包括表结构
B.删除当前数据库中employee表内的所有行
C.由于没有where子句,因此不删除任何数据
D.删除当前数据库中employee表内的当前行
第1题:
已知employee表中具有默认约束df_email,删除该约束的语句为_________。
A.alter table employee drop constraint df_email
B.alter table employee remove constraint df_email
C.alter table employee delete constraint df_email
D.remove constraint df_email from table employee
第2题:
已知employee表中有默认约束de_email,删除该约束的语句为()
A.Alter table employee drop df_email
B.Alter table employee remove df_email
C.Alter table employee delete df_email
D.remove df_email from table employee
第3题:
已知employee表中具有约束df_email,删除该约束的语句为_________。
A.alter table employee drop constraint df_email
B.alter table employee remove constraint df_email
C.alter table employee delete constraint df_email
D.remove constraint df_email from table employee
第4题:
已知employee表中具有默认约束df_email,删除该约束的语句为_________。
A.remove constraint df_email from table employee
B.alter table employee remove constraint df_email
C.alter table employee drop constraint df_email
D.alter table employee delete constraint df_email
第5题:
4、已知employee表中具有默认约束df_email,删除该约束的语句为_________。
A.alter table employee drop constraint df_email
B.alter table employee remove constraint df_email
C.alter table employee delete constraint df_email
D.remove constraint df_email from table employee