【简答题】放大镜实际上就是一只______镜,我们通过放大镜看到物体的像是______、______、______像;使用时,必须将物体放在透镜的______以内.
【单选题】In a university database, the student table, with student ID as a primary key, is linked to the university department table through its primary key-department ID. In the student table, department ID i...
【单选题】“至今一切社会的历史都是阶级斗争的历史”这句话源于( )
【多选题】下列属于从开展电子交易的信息网络范围角度,电子商务可以分为()
【单选题】A primary key in a database is a ________.
A.
group of rows that identifies a unique table or file
B.
column or group of columns that identifies a unique row in a table
C.
group of fields or columns that represent metadata
D.
group of tables or files formed to identify a unique field or row
E.
group of records that identifies similar attribute
【单选题】“至今一切社会的历史都是阶级斗争的历史”这句话源于?
【判断题】A foreign key is an attribute in a table that is a primary key in another table.
【简答题】误区:放大镜只能成放大的像.放大镜实际上就是一个______透镜,只是利用了物体在______成放大的虚像这一原理.放大镜也可以成______像.