PHP Interview questions 16

61) What are the other commands to know the structure of table using MySQL commands except explain command?

Ans :      describe Table-Name;

                 

62) How many tables will create when we create table, what are they?

Ans :      The '.frm' file stores the table definition.

The data file has a '.MYD' (MYData) extension.

The index file has a '.MYI' (MYIndex) extension,

                 

 63) What is the purpose of the following files having extensions 1) .frm 2) .myd 3) .myi? What do these files contain?

Ans :      In MySql, the default table type is MyISAM.

Each MyISAM table is stored on disk in three files. The files have names that begin with the table name and have an extension to indicate the file type.

The '.frm' file stores the table definition.

The data file has a '.MYD' (MYData) extension.

The index file has a '.MYI' (MYIndex) extension,

64) What is maximum size of a database in MySQL?

Ans :      If the operating system or filesystem places a limit on the number of files in a directory, MySQL is bound by that constraint.The efficiency of the operating system in handling large numbers of files in a directory can place a practical limit on the number of tables in a database. If the time required to open a file in the directory increases significantly as the number of files increases, database performance can be adversely affected.

The amount of available disk space limits the number of tables.

MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage engine in MySQL 3.23, the maximum table size was increased to 65536 terabytes (2567 – 1 bytes). With this larger allowed table size, the maximum effective table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits.The InnoDB storage engine maintains InnoDB tables within a tablespace that can be created from several files. This allows a table to exceed

the maximum individual file size. The tablespace can include raw disk partitions, which allows extremely large tables. The maximum tablespace size is 64TB.

The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive. For the most up-to-date information, be sure to check the documentation specific to your operating system.

Operating System File-size LimitLinux 2.2-Intel 32-bit 2GB (LFS: 4GB)

Linux 2.4+ (using ext3 filesystem) 4TB

Solaris 9/10 16TB

NetWare w/NSS filesystem 8TB

Win32 w/ FAT/FAT32 2GB/4GB

Win32 w/ NTFS 2TB (possibly larger)

MacOS X w/ HFS+ 2TB

65) Give the syntax of Grant and Revoke commands?

Ans :      The generic syntax for grant is as following

> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY [password] now rights can be

a) All privileges

b) combination of create, drop, select, insert, update and delete etc.We can grant rights on all databse by using *.* or some specific database by database.* or a specific table by database.table_name

username@hotsname can be either username@localhost, username@hostname and username@%

where hostname is any valid hostname and % represents any name, the *.* any condition password is simply the password of userThe generic syntax for revoke is as following > REVOKE [rights] on  [database/s] FROM [username@hostname] now rights can be as explained above

a) All privileges

b) combination of create, drop, select, insert, update and delete etc.

username@hotsname can be either username@localhost, username@hostname and username@%

where hostname is any valid hostname and % represents any name, the *.*

any condition