Dell Boomi Most Frequently Asked MySQL Interview Questions

Dell Boomi Most Frequently Asked Latest MySQL Interview Questions Answers

How To Use Like Conditions?

A LIKE condition is also called pattern patch. There are 3 main rules on using LIKE condition:

is used in the pattern to match any one character.
% is used in the pattern to match any zero or more characters.
ESCAPE clause is used to provide the escape character in the pattern.

How To Present A Past Time In Hours, Minutes And Seconds?

If you want show an article was posted “n hours n minutes and n seconds ago’, you can use the TIMEDIFF(NOWO, pastTime) function as shown in the following are:

SELECT TIMEDIFF(NOWO, ‘2006-07-01 04:09:49’) FROM DUAL;
06:42:58
SELECT TIM E_FORMAT(TI M EDI FF( NOWO, ‘2006-06-30 04:09:49’),
 ‘%H hours, %i minutes and %s seconds ago.’) FROM DUAL;
30 hours, 45 minutes and 22 seconds ago.

How To Add A New Column To An Existing Table In Mysql?

ALTER TABLE tip ADD COLUMN author VARCHAR(40);
Query OK, 1 row affected (0.18 sec)
Records: 1 Duplicates: 0 Warnings: 0

Dell Boomi Most Frequently Asked Latest MySQL Interview Questions Answers

How To Delete An Existing Column In A Table?

ALTER TABLE tip DROP COLUMN create_date;
Query OK, 1 row affected (0.48 sec)
Records: 1 Duplicates: 0 Warnings: 0

How To Rename An Existing Column In A Table?

ALTER TABLE tip CHANGE COLUMN subject title VARCHAR(60);

How To Rename An Existing Table In Mysql?

ALTER TABLE tip RENAME TO faq;

How To Create A Table Index In Mvsql?

If you have a table with a lots of rows, and you know that one of the columns will be used often as a search criteria, you can add an index for that column to improve the search performance. To add an index, you can use the “CREATE INDEX” statement as shown in the following script:

<pre>mysql> CREATE TABLE tip (id INTEGER PRIMARY KEY,
subject VARCHAR(80) NOT NULL,
description VARCHAR(256) NOT NULL,
create_date DATE NULL);  Query OK,
0 rows affected (0.08 sec)</pre>
mysql> CREATE INDEX tip_subject ON tip(subject);
Query OK,
0 rows affected (0.19 sec)
Records: 0 Duplicates: 0 Warnings: 0

How To Get A List Of Indexes Of An Existing Table?

If you want to see the index you have just created for an existing table, you can use the “SHOW INDEX FROM tableName” command to get a list of all indexes in a given table.

How To Drop An Existing Index In Mysql?

If you don’t need an existing index any more, you should delete it with the “DROP INDEX indexName ON tableName” statement. Here is an example SQL script :

mysqi> DROP INDEX tip_subject ON tip;
Query OK, 0 rows affected (0.13 sec)
Records: 0 Duplicates: 0 Warnings: 0

How To Drop An Existing View In Mysql?

If you have an existing view, and you dont want it anymore, you can delete it by using the “DROP VIEW viewName” statement

How To Create A New View In Mysql?

You can create a new view based on one or more existing tables by using the

“CREATE VIEW viewName AS selectStatement” .

How To Increment Dates By 1111 Mysql?

If you have a date, and you want to increment it by 1 day, you can use the DATE_ADD(date, INTERVAL 1 DAY) function. You can also use the date interval add operation as “date + INTERVAL 1 DAY.

Differentiate between FLOAT and DOUBLE?

Following are differences for FLOAT and DOUBLE:

• Floating point numbers are stored in FLOAT with eight place accuracy and it has four bytes.


• Floating point numbers are stored in DOUBLE with accuracy of 18 places and it has eight bytes.

 Differentiate CHAR_LENGTH and LENGTH?

CHAR_LENGTH  is character count whereas the LENGTH is byte count. The numbers are same for Latin characters but they are different for Unicode and other encodings.

How to represent ENUMs and SETs internally?

ENUMs and SETs are used to represent powers of two because of storage optimizations.

What is the usage of ENUMs in MySQL?

ENUM is a string object used to specify set of predefined values and that can be used during table creation.

Create table size(name ENUM('Small', 'Medium','Large');
1
Create table size(name ENUM('Small', 'Medium','Large');