Tuesday, 10 February 2015

PHP-MySQL Interview Question and Answers pdf (Page 2)

Below are some important MySQL interview questions which are asked in most MNC company interviews for beginners or professionals.

6. What Is Union?
Join is data retrieval operation that combines multiple query outputs of the same structure into a single output. By default the MySQL UNION removes all duplicate rows from the result set even if you don’t explicit using DISTINCT after the keyword UNION.
SELECT customerNumber id, contactLastname name
FROM customers
SELECT employeeNurrber id, firstname name
FROM employees
id name
103 Schmitt
112 King
114 Ferguson
119 Labrune
121 Bergulfsen

7. What Is ISAM?
ISAM (Indexed Sequential Access Method) was developed by IBM to store and retrieve data on secondary storage systems like tapes.

8. What Is InnoDB?
lnnoDB is a transaction safe storage engine developed by Innobase Oy (an Oracle company now).
What Is BDB (BerkeleyDB)?
BDB (BerkeleyDB) is transaction safe storage engine originally developed at U.C. Berkeley. It is now developed by Sleepycat Software, Inc. (an Oracle company now).

9. What Is CSV?
CSV (Comma Separated Values) is a file format used to store database table contents, where one table row is stored as one line in the file, and each data field is separated with comma.

10. What Is Transaction?
A transaction is a logical unit of work requested by a user to be applied to the database objects. MySQL server introduces the transaction concept to allow users to group one or more SQL statements into a single transaction, so that the effects of all the SQL statements in a transaction can be either all committed (applied to the database) or all rolled back (undone from the database).
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