MySQL Interview Question Set 2

11. Define REGEXP?
REGEXP is a pattern match in which matches pattern anywhere in the search value.

12. Difference between CHAR and VARCHAR?
Following are the differences between CHAR and VARCHAR:

  • CHAR and VARCHAR types differ in storage and retrieval
  • CHAR column length is fixed to the length that is declared while creating table. The length value ranges from 1 and 255
  • When CHAR values are stored then they are right padded using spaces to specific length. Trailing spaces are removed when CHAR values are retrieved.

13. Give string types available for column?
The string types are:

  • SET
  • BLOB
  • ENUM
  • CHAR
  • TEXT

14. How to get current MySQL version?
SELECT VERSION ();is used to get the current version of MySQL.

15. What storage engines are used in MySQL?
Storage engines are called table types and data is stored in files using various techniques.
Technique involves:

  • Storage mechanism
  • Locking levels
  • Indexing
  • Capabilities and functions.

16. What are the drivers in MySQL?
Following are the drivers available in MySQL:

  • PHP Driver
  • JDBC Driver
  • ODBC Driver
  • PYTHON Driver
  • PERL Driver
  • RUBY Driver
  • CAP11PHP Driver
  • Ado.net5.mxj

17. What does a TIMESTAMP do on UPDATE CURRENT_TIMESTAMP data type?
TIMESTAMP column is updated with Zero when the table is created. UPDATE CURRENT_TIMESTAMP modifier updates the timestamp field to current time whenever there is a change in other fields of the table.

18. What is the difference between primary key and candidate key?
Every row of a table is identified uniquely by primary key. There is only one primary key for a table. Primary Key is also a candidate key. By common convention, candidate key can be designated as primary and which can be used for any foreign key references.

19. How do you login to MySql using Unix shell?
We can login through this command:
# [mysql dir]/bin/mysql -h hostname -u -p

20. What does myisamchk do?
It compress the MyISAM tables, which reduces their disk or memory usage.

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