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people:hr:good-technical-interview-questions:mysql-questions [Sep 8, 2010 01:11 AM]
dordal 		people:hr:good-technical-interview-questions:mysql-questions [Jun 27, 2023 03:57 PM]
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 += MySQL Interview Questions =
 + * Explain the basic CRUD operations (CREATE, UPDATE, DELETE) and how you'd use SQL to perform them.
 + * Explain the ''WHERE'' clause on a ''SELECT'' statement, what it does and how it works.
 + * Explain ''GROUP BY''. What does it do, and when do you have to use it?
 + * What is a view? Why would you want to use one?
 + * What is a trigger? Why are triggers good and bad?
 + * What's an index? Advanced: What are the different types of indexes?
 + * What's a foreign key? What does the ''ON CASCADE'' clause do when creating a foreign key?
 + * Explain what a transaction is, when you'd want to use one, and when you probably //wouldn't// want to use one.
 + * Explain the MySQL architecture (e.g. the three layers... networking/connection layer, query parsing, and the storage engine)
 + * Explain the differences between InnoDB and MyISAM. When would you want to use each?
 + * Talk to me about the process you'd use for optimizing an SQL query. 
 + * What's the difference between ''CHAR'', ''VARCHAR'', ''TEXT'' and ''BLOB'' datatypes?
 + * Is there anything special about ''NULL'' values in MySQL (or SQL in general?) How do you test for a ''NULL'' value?
 + * What's the difference between a ''TIMESTAMP'' field and a ''DATETIME'' field? Advanced question: can you describe the different handling of timezones between ''TIMESTAMP'' and ''DATETIME''?
 + * Explain locking principles in MySQL. Table level locks, page-level locks, and row-level locks. Which storage engines can do which? Explain what [[http://dev.mysql.com/doc/refman/5.0/en/innodb-lock-modes.html|shared vs. exclusive locks]] are.
 + * Why does ''DELETE FROM `mytable`'' run very quickly, whereas ''DELETE FROM `mytable` WHERE 1=1'' run very slowly, if 'mytable' has a large number of records? (e.g. the former just deletes and recreates the table on disk, whereas the latter will delete each row one-by-one.)
  
 +== PHP/MySQL Questions ==
 + * Explain the difference between the standard MySQL libraries (e.g. mysql_connect() ) and the MySQLi libraries (e.g. mysqli_connect() ) 
 + * Walk me through the basic process for connecting to a MySQL database and querying some information.