My SQL Interview Questions and Answers - Part 3

[VelMurugan]

My SQL Interview Questions and Answers

How are ENUMs and SETs represented internally?

As unique integers representing the powers of two, due to storage optimizations.

How do you start and stop MySQL on Windows?

net start MySQL, net stop MySQL

How do you start MySQL on Linux?

/etc/init.d/mysql start

Explain the difference between mysql and mysql interfaces in PHP?

mysqli is the object-oriented version of mysql library functions.

What's the default port for MySQL Server?

3306

What does tee command do in MySQL?

tee followed by a filename turns on MySQL logging to a specified file. It can be stopped by command note.

Can you save your connection settings to a conf file?

Yes, and name it ~/.my.conf. You might want to change the permissions on the file to 600, so that it's not readable by others.

How do you change a password for an existing user via mysqladmin?

mysqladmin -u root -p password "newpassword"

Use mysqldump to create a copy of the database?

mysqldump -h mysqlhost -u username -p mydatabasename > dbdump.sql

Have you ever used MySQL Administrator and MySQL Query Browser?

Describe the tasks you accomplished with these tools.

What are some good ideas regarding user security in MySQL?

There is no user without a password. There is no user without a user name. There is no user whose Host column contains % (which here indicates that the user can log in from anywhere in the network or the Internet). There are as few users as possible (in the ideal case only root) who have unrestricted access.

Explain the difference between MyISAM Static and MyISAM Dynamic. ?

In MyISAM static all the fields have fixed width. The Dynamic MyISAM table would include fields such as TEXT, BLOB, etc. to accommodate the data types with various lengths. MyISAM Static would be easier to restore in case of corruption, since even though you might lose some data, you know exactly where to look for the beginning of the next record.

What does myisamchk do?

It compressed the MyISAM tables, which reduces their disk usage.

Explain advantages of InnoDB over MyISAM?

Row-level locking, transactions, foreign key constraints and crash recovery.

Explain advantages of MyISAM over InnoDB?

Much more conservative approach to disk space management - each MyISAM table is stored in a separate file, which could be compressed then with myisamchk if needed. With InnoDB the tables are stored in tablespace, and not much further optimization is possible. All data except for TEXT and BLOB can occupy 8,000 bytes at most. No full text indexing is available for InnoDB. TRhe COUNT(*)s execute slower than in MyISAM due to tablespace complexity.