SQL - கேள்வி பதில் பகுதி - 3

Q 21 Explain what a full join is.

A A full join combines the behavior of a left outer join and a right outer join. An example is where you show all customers whether or not they have orders, and all orders whether or not they are associated with a customer.

Q 22 Explain the difference between the HAVING clause and the WHERE clause.

A SQL Server Express applies the HAVING clause after it summarizes the data, whereas it applies the WHERE clause before it summarizes the data.

Q 23  Describe a subquery.

A SQL Server Express evaluates a subquery before it evaluates the main query.

Q24  Explain the difference between INSERT and SELECT INTO.

A INSERT adds data to an existing table, whereas SELECT INTO creates a new table containing the data that you are inserting.

Q 25 Explain the difference between a DELETE statement and a trUNCATE statement.

A A DELETE statement enables you to selectively remove data from a table, whereas the TRUNCATE statement unconditionally removes all rows from a table.

Q 26 Describe the difference between trUNCATE and DROP.

A trUNCATE removes all data from the table while retaining the table structure, whereas DROP removes the table from the database.

Q 27 Explain what the STUFF function does.

A The STUFF function starts at a certain position and replaces a specified number of characters with other specified characters.

Q 28 Explain what the DATEPART function does.

A The DATEPART function extracts part of a date. You designate the part of the date you want to extract, and the date from which you want to extract it.

Q 29 Explain the ISNULL function.

A The ISNULL function returns information about whether the value in an expression is null. It receives the expression that you want to evaluate, and the value that you want to return if the expression is null. It returns the specified value.

Q 30. Name some advantages of views.

A. Views enable you to join data, aggregate data, customize data to the user's needs, hide underlying column names from users, limit the columns and rows that a user works with, and easily secure data.