How To Concatenate Two Character Strings?
If you want concatenate multiple character strings into one, you need to use the CONCAT() function. Here are some good examples:
SELECT CONCAT(’Welcome’,’ to’) FROM DUAL;
Welcome to
SELECT CONCAT(wj’,’center’,’.com’) FROM DUAL;
wisdomjobs.com
How To Enter Characters As Hex Numbers?
If you want to enter characters as HEX numbers, you can quote HEX numbers with single quotes and a prefix of (X), or just prefix HEX numbers with (Ox). A HEX number string will be automatically converted into a character string, if the expression context is a string. Here are some good examples:
SELECT X313233’ FROM DUAL;
123
SELECT 0x414243 FROM DUAL;
ABC
How To Enter Boolean Values In Sql Statements?
If you want to enter Boolean values in SQL statements, you use (TRUE), (FALSE), (true), or (false). Here are some good examples:
SELECT TRUE, true, FALSE, false FROM DUAL;
How To Convert Numeric Values To Character Strings?
You can convert numeric values to character strings by using the CAST(value AS CHAR) function as shown in the following examples:
SELECT CAST(4123.45700 AS CHAR) FROM DUAL;
4123.45700
How To Get Rid Of The Last 2 0's?
SELECT CAST(4.12345700E+3 AS CHAR) FROM DUAL;
4123.457
SELECT CAST(1/3 AS CHAR);
0.3333
How To Use In Conditions?
An IN condition is single value again a list of values. It returns TRUE, if the specified value is in the list. Otherwise, it returns FALSE. Some examples are :
SELECT 3 IN (1,2,3,4,5) FROM DUAL;
1
SELECT 3 NOT IN (1,2,3,4,5) FROM DUAL;
0
SELECT Y’ IN (‘F’,’Y’,I) FROM DUAL;
1
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
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');
Define REGEXP?
REGEXP is a pattern match in which matches pattern anywhere in the search value.
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.
What are the technical features of MySQL?
MySQL database software is a client or server system which includes
Multithreaded SQL server supporting various client programs and libraries
Different backend
Wide range of application programming interfaces and
Administrative tools.
Why MySQL is used?
MySQL database server is reliable, fast and very easy to use. This software can be downloaded as freeware and can be downloaded from the internet.
If you want concatenate multiple character strings into one, you need to use the CONCAT() function. Here are some good examples:
SELECT CONCAT(’Welcome’,’ to’) FROM DUAL;
Welcome to
SELECT CONCAT(wj’,’center’,’.com’) FROM DUAL;
wisdomjobs.com
How To Enter Characters As Hex Numbers?
If you want to enter characters as HEX numbers, you can quote HEX numbers with single quotes and a prefix of (X), or just prefix HEX numbers with (Ox). A HEX number string will be automatically converted into a character string, if the expression context is a string. Here are some good examples:
SELECT X313233’ FROM DUAL;
123
SELECT 0x414243 FROM DUAL;
ABC
How To Enter Boolean Values In Sql Statements?
If you want to enter Boolean values in SQL statements, you use (TRUE), (FALSE), (true), or (false). Here are some good examples:
SELECT TRUE, true, FALSE, false FROM DUAL;
 |
| Deloitte MySQL Most Frequently Asked Latest Interview Questions Answers |
How To Convert Numeric Values To Character Strings?
You can convert numeric values to character strings by using the CAST(value AS CHAR) function as shown in the following examples:
SELECT CAST(4123.45700 AS CHAR) FROM DUAL;
4123.45700
How To Get Rid Of The Last 2 0's?
SELECT CAST(4.12345700E+3 AS CHAR) FROM DUAL;
4123.457
SELECT CAST(1/3 AS CHAR);
0.3333
How To Use In Conditions?
An IN condition is single value again a list of values. It returns TRUE, if the specified value is in the list. Otherwise, it returns FALSE. Some examples are :
SELECT 3 IN (1,2,3,4,5) FROM DUAL;
1
SELECT 3 NOT IN (1,2,3,4,5) FROM DUAL;
0
SELECT Y’ IN (‘F’,’Y’,I) FROM DUAL;
1
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
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');
Define REGEXP?
REGEXP is a pattern match in which matches pattern anywhere in the search value.
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.
What are the technical features of MySQL?
MySQL database software is a client or server system which includes
Multithreaded SQL server supporting various client programs and libraries
Different backend
Wide range of application programming interfaces and
Administrative tools.
Why MySQL is used?
MySQL database server is reliable, fast and very easy to use. This software can be downloaded as freeware and can be downloaded from the internet.
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