Building Database Applications in PHP Week 2 Practice Quiz Answers
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Building Database Applications in PHP Week 2 Practice Quiz Answer
Question 1) Why is it important to have extensive error checking on SQL statements when an application is in production?
- Tracebacks make your application look bad
- The developer/production team needs good detail on any errors
- Users will rarely report errors and never give enough detail
- Some errors are subtle and only show up very rarely
- All of the above
Question 2)What is the purpose of the PDO::errorinfo() data?
- It combines the prepare() and execute() phases of PDO into a single call
- It allows you to choose the style of error handling for your application
- It allows you to register a callback function to be called in case of an unhandled error
- It gives extended detail when a PDO function returns an error
Question 3) How is a LEFT JOIN different from a regular JOIN?
- In a LEFT JOIN rows can come from either the left table or right table as long as the row matches the WHERE clause
- All of the text fields are left aligned in the result set
- In a LEFT JOIN rows are included form the left table even if there is no matching row in the right table
- You do not need an ON clause for the LEFT JOIN
Question 4) What is a common use of GROUP BY in SQL?
- When combined with the COUNT function, it provides a way to compute sub-totals
- It is a faster way to sort fields than ORDER BY
- It is a way to choose which rows from a JOINed table are to be included in a result set
- It allows a result set to be broken into 20 row chunks for efficiency
Question 5) Why do subqueries have the potential to cause a query to execute slowly?
- Because subqueries don’t make use of indexes
- Because subqueries cannot use integer foreign keys
- Because subqueries must include all of the fields that are selected by the main query
- Because MySQL executes the subquery independently from the main query