Database-MySQL [3i Infotech Placement]: Sample Questions 103 - 105 of 162
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Question 103
Describe in Detail Essay▾
What command is used to create a table by copying the structure of another table?
EditExplanation
- CREATE TABLE … . AS SELECT command creates a table by copying the structure of another table.
- If WHERE clause of the SELECT command contains a FALSE statement- the statement only copies structure:
CREATE TABLE NEWTABLE AS SELECT ⚹ FROM EXISTING TABLE WHERE 1 = 2;
- The where condition is true, then all the rows satisfying the condition will be copied to the new table.
- SQL SELECT statement retrieves data from a table in the database.
- Query may retrieve information from specified columns or from all rows in the table.
Question 105
Explanation
- A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table.
- In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
- Growth and restructuring of base tables is not reflected in views.
- Thus the view can insulate users from the effects of restructuring and growth in the database.
- Hence accounts for logical data independence.