Answer: D) None of the above
Explanation: The subschema differs from the schema in that one denotes the appearance of data in the Database Base Management System (DBMS) while the subschema which is also referred to as the external schema is that subset of the schema is visible or relevant to the user. Thus, It is the view of the database which is visible to an application program. Virtual tables in a database usually represents an object structures like a table which is the result of running certain database commands or functions such as the create table, view, select and so on. Virtual tables are not stored directly in database files.
Answer:
Explanation:
Mực nước biển dâng cao, nhiều lục địa lớn nhất dần dần bị nhấn chìm, hiện tượng tan băng còn giải phóng nhiều loại virus cổ đại nguy hiểm, các hoạt động khai thác trên biển của con người gặp khó khăn
Answer:
The terra firma plays a crucial politics role within the Arab world because of its huge reserves of oil and fossil fuel. Before the fashionable era, it had been divided into four distinct regions: sea Coast (Tihamah), Central highland (Al-Yamama), ocean Coast (Hadhramaut) and Persian Gulf Coast (Al-Bahrain).
Explanation:
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<span>The policy of eradication has caused 1.75 million acres of Amazon rainforest to be cleared.
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He tells wiglaf that he must now look after the gears and order his troop to build him a barrel that will call him "beowulfs barrow" after giving wiglaf the collar from his own neck. Beowulf dies
