Databases Questions & Answers

　　1.What are two methods of retrieving SQL?

　　Answer:

　　暂缺

　　2.What cursor type do you use to retrieve multiple recordsets?

　　Answer:

　　暂缺

　　3.What action do you have to perform before retrieving data from the next result set of a stored procedure?

　　Answer:

　　Move the cursor down one row from its current position. A ResultSet cursor is initially positioned before the first row. Before you can get to the first row, you would need to Move the cursor down by one row ( For ex: in java the first call to next makes the first row the current row; the second call makes the second row the current row, and so on).

　　4.What is the basic form of a SQL statement to read data out of a table?

　　Answer: SELECT * FROM table_name;

　　5.What structure can you have the database make to speed up table reads?

　　Answer:

　　The question is not correct. "What structure can you have the database make to speed up table reads?" It is not clear what exactly the term "structure" means in this case. Follow the rules of DB tuning we have to:

　　1) properly use indexes ( different types of indexes)

　　2) properly locate different DB objects across different tablespaces, files and so on.

　　3) Create a special space (tablespace) to locate some of the data with special datatypes( for example CLOB, LOB and ...)

　　4)...

　　5)...

　　6.What is a "join"?

　　Answer:

　　Joins merge the data of two related tables into a single result set, presenting a denormalized view of the data.