MySQL interview questions (4)

61.Mysql What storage engine is used in ？

The storage engine is called a table type , Data is stored in files using various techniques .
Technology involves ：
Storage mechanism
Locking levels
Indexing
Capabilities and functions.

62.Mysql What is the driver ？

Here are Mysql Drivers available in ：
PHP The driver
JDBC The driver
ODBC The driver
CWRAPPER
PYTHON The driver
PERL The driver
RUBY The driver
CAP11PHP The driver
Ado.net5.mxj

63.TIMESTAMP stay UPDATE CURRENT_TIMESTAMP What to do with data types ？

Create table time TIMESTAMP Column use Zero to update . As long as other fields in the table change ,UPDATE CURRENT_TIMESTAMP The Modifier updates the timestamp field to the current time .

64. What's the difference between a primary key and a candidate key ？

Each row of the table is uniquely identified by the primary key , A table has only one primary key .
The primary key is also a candidate key . By convention , Candidate keys can be specified as primary keys , And can be used for any foreign key reference .

65. How to use Unix shell Sign in Mysql？

We can log in with the following command ：
[mysql dir]/bin/mysql -h hostname -u -p

66.myisamchk What is it used for ？

It's used to compress MyISAM surface , This reduces disk or memory usage .

67.、 How to control HEAP The maximum size of the watch ？

Heal The size of the table can be determined by calling max_heap_table_size Of Mysql Configure variables to control .

68.MyISAM Static and MyISAM Dynamic What's the difference? ？

stay MyISAM Static All fields on have a fixed width . dynamic MyISAM The watch will have a look like TEXT,BLOB Etc , To accommodate different length data types .
MyISAM Static Easier to recover in case of damage .

69.federated What is a watch ？

federated surface , Allow access to tables located on other server databases .

70. If a table has a column defined as TIMESTAMP, What will happen ？

Every time a line is changed , The timestamp field will get the current timestamp .