下面哪条命令能够保证只删除表employee.的数据而保留表的结构并且必要是可以回滚?()
A. DROP TABLE employee.
B. DELETE FROM employee.
C. TRUNCATE TABLE employee.
D. This task can’t be accomplished.
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语句 WHERE SAL BETWEEN 1000 AND 4000 与下列哪个子句等价()
A. WHERE SAL〉=1000 AND SAL﹤=4000
B. WHERE SAL〉1000 AND SAL﹤4000
C. WHERE SAL〉=1000 OR SAL﹤=4000
D. WHERE SAL〉=1000 AND SAL ﹤4000
查询语句SELECT ROUND(13.57),ROUND13.57,1),ROUND(13.57,-1),TRUNC(13.57,-2) FROM DUAL 返回结果,正确的是()
A. 13.57,13.6,10,13
B. 13,13.5,14,0
C. 14,13.6,10,0
D. 13.6,13.5,11,13
SQL语句中连接字符串的符号是()
A. “+”
B. “||”
C. “|”
D. “&
查询语句SELECT SUBSTR(‘Hello World’,4,5) FROM DUAL;返回结果,正确的是()
A. loWor
B. World
C. lloWo
D. lo Wo
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