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MYSQL CONFIG VARIABLE max_heap_table_size.

MySQL config variable max_heap_table_size.

HEAP tables are in-memory. They are usually used for high-speed temporary storage. No TEXT or
BLOB fields are allowed within HEAP tables. You can only use the COMPARISON operators = and <=>. HEAP tables do not SUPPORT AUTO_INCREMENT. INDEXES must be NOT NULL.

HEAP tables are in-memory. They are usually used for high-speed temporary storage. No TEXT or
BLOB fields are allowed within HEAP tables. You can only use the comparison operators = and <=>. HEAP tables do not support AUTO_INCREMENT. Indexes must be NOT NULL.

Much more conservative approach to disk space management - each MyISAM table is stored in a SEPARATE file, which could be compressed then with myisamchk if needed. With INNODB the tables are stored in tablespace, and not much further optimization is possible. All data except for TEXT and BLOB can occupy 8,000 BYTES at most. No full text indexing is available for InnoDB. TRhe COUNT(*)s EXECUTE slower than in MyISAM DUE to tablespace complexity.

Much more conservative approach to disk space management - each MyISAM table is stored in a separate file, which could be compressed then with myisamchk if needed. With InnoDB the tables are stored in tablespace, and not much further optimization is possible. All data except for TEXT and BLOB can occupy 8,000 bytes at most. No full text indexing is available for InnoDB. TRhe COUNT(*)s execute slower than in MyISAM due to tablespace complexity.

Row-level LOCKING, transactions, foreign KEY constraints and CRASH recovery.

Row-level locking, transactions, foreign key constraints and crash recovery.

It COMPRESSED the MYISAM TABLES, which reduces their disk USAGE.

It compressed the MyISAM tables, which reduces their disk usage.

In MyISAM STATIC all the fields have fixed width. The Dynamic MyISAM table WOULD include fields such as TEXT, BLOB, ETC. to accommodate the data types with various lengths. MyISAM Static would be easier to restore in case of corruption, since even though you MIGHT lose some data, you know exactly where to look for the beginning of the next record.

In MyISAM static all the fields have fixed width. The Dynamic MyISAM table would include fields such as TEXT, BLOB, etc. to accommodate the data types with various lengths. MyISAM Static would be easier to restore in case of corruption, since even though you might lose some data, you know exactly where to look for the beginning of the next record.

There is no user without a password. There is no user without a user name. There is no user whose Host column contains % (which here indicates that the user can log in from anywhere in the NETWORK or the INTERNET). There are as few users as POSSIBLE (in the ideal CASE only root) who have unrestricted access.

There is no user without a password. There is no user without a user name. There is no user whose Host column contains % (which here indicates that the user can log in from anywhere in the network or the Internet). There are as few users as possible (in the ideal case only root) who have unrestricted access.

DESCRIBE the TASKS you ACCOMPLISHED with these TOOLS.

Describe the tasks you accomplished with these tools.

<P>MYSQLDUMP -h mysqlhost -u USERNAME -p mydatabasename &GT; dbdump.sql

mysqldump -h mysqlhost -u username -p mydatabasename > dbdump.sql

<P>MYSQLADMIN -U ROOT -p PASSWORD "newpassword"

mysqladmin -u root -p password "newpassword"

Yes, and name it ~/.my.conf. You might WANT to change the PERMISSIONS on the FILE to 600, so that it’s not READABLE by others.

Yes, and name it ~/.my.conf. You might want to change the permissions on the file to 600, so that it’s not readable by others.

TEE FOLLOWED by a filename TURNS on MySQL logging to a specified file. It can be stopped by COMMAND note.

tee followed by a filename turns on MySQL logging to a specified file. It can be stopped by command note.

3306 is the DEFAULT PORT for MYSQL.

3306 is the default port for MYSQL.

MYSQL is the object-oriented VERSION of mysql LIBRARY FUNCTIONS.

mysql is the object-oriented version of mysql library functions.

/etc/init.d/mysql START

/etc/init.d/mysql start

NET START MYSQL, net STOP MySQL

net start MySQL, net stop MySQL

As UNIQUE INTEGERS REPRESENTING the POWERS of two, due to storage optimizations.

As unique integers representing the powers of two, due to storage optimizations.

You can limit the possible values that go into the table. CREATE TABLE MONTHS (month ENUM ‘January’, ‘FEBRUARY’, ‘March’,…); INSERT months VALUES (’APRIL’);

You can limit the possible values that go into the table. CREATE TABLE months (month ENUM ‘January’, ‘February’, ‘March’,…); INSERT months VALUES (’April’);

UNIX_TIMESTAMP CONVERTS from MYSQL TIMESTAMP to UNIX timestamp, FROM_UNIXTIME converts from Unix timestamp to MySQL timestamp.

UNIX_TIMESTAMP converts from MySQL timestamp to Unix timestamp, FROM_UNIXTIME converts from Unix timestamp to MySQL timestamp.

INTERNALLY Unix TIMESTAMPS are stored as 32-bit integers, while MySQL timestamps are stored in a similar manner, but REPRESENTED in readable YYYY-MM-DD HH:MM:SS format.

Internally Unix timestamps are stored as 32-bit integers, while MySQL timestamps are stored in a similar manner, but represented in readable YYYY-MM-DD HH:MM:SS format.

ADDDATE(techpreparation_publication_date, INTERVAL 3 MINUTE)

ADDDATE(techpreparation_publication_date, INTERVAL 3 MINUTE)

SELECT DATE_FORMAT(techpreparation_timestamp, ‘%Y-%m-%d’) from techpreparation_questions; A SIMILAR TIME_FORMAT FUNCTION DEALS with TIME.

SELECT DATE_FORMAT(techpreparation_timestamp, ‘%Y-%m-%d’) from techpreparation_questions; A similar TIME_FORMAT function deals with time.

SELECT MONTH(techpreparation_timestamp) from techpreparation_questions;

SELECT MONTH(techpreparation_timestamp) from techpreparation_questions;

At least one character. APPENDIX G. Regular EXPRESSIONS from MYSQL manual is WORTH perusing before the interview.

At least one character. Appendix G. Regular Expressions from MySQL manual is worth perusing before the interview.

% CORRESPONDS to 0 or more characters, _ is EXACTLY one character.

% corresponds to 0 or more characters, _ is exactly one character.

SELECT (techpreparation_question USING UTF8);

SELECT (techpreparation_question USING utf8);

The first is, NATURALLY, the character COUNT. The second is byte count. For the LATIN characters the numbers are the same, but they’re not the same for Unicode and other encodings.

The first is, naturally, the character count. The second is byte count. For the Latin characters the numbers are the same, but they’re not the same for Unicode and other encodings.

SELECT SUBSTR(TITLE, 1, 10) from techpreparation_questions;

SELECT SUBSTR(title, 1, 10) from techpreparation_questions;

CONCAT (STRING1, STRING2, string3)

CONCAT (string1, string2, string3)

SHOW DATABASES LIKE ‘TECH%’;

SHOW DATABASES LIKE ‘tech%’;

1. VARCHARs with LENGTH less than 4 BECOME CHARs
2. CHARs with length more than 3 become VARCHARs.
3. NOT NULL gets added to the columns declared as PRIMARY KEYS
4. Default values such as NULL are SPECIFIED for each column

1. VARCHARs with length less than 4 become CHARs
2. CHARs with length more than 3 become VARCHARs.
3. NOT NULL gets added to the columns declared as PRIMARY KEYs
4. Default values such as NULL are specified for each column

ALTER TABLE techpreparation_questions ENGINE INNODB;

ALTER TABLE techpreparation_questions ENGINE innodb;

ALTER TABLE techpreparation_answers DROP answer_user_id.

ALTER TABLE techpreparation_answers DROP answer_user_id.

ALTER TABLE techpreparation_questions CHANGE techpreparation_content techpreparation_CONTENT VARCHAR(50).

ALTER TABLE techpreparation_questions CHANGE techpreparation_content techpreparation_CONTENT VARCHAR(50).

SHOW INDEX FROM techpreparation_questions;

SHOW INDEX FROM techpreparation_questions;

When you’re not deleting by row ID. Such as in DELETE FROM techpreparation_com_questions ORDER BY timestamp LIMIT 1.

When you’re not deleting by row ID. Such as in DELETE FROM techpreparation_com_questions ORDER BY timestamp LIMIT 1.

What it means is that so of the DATA that you’re trying to DELETE is still alive in another table. Like if you have a table for universities and a table for students, which contains the ID of the university they go to, running a delete on a university table will fail if the students table still contains people enrolled at that university. Proper way to do it would be to delete the offending data FIRST, and then delete the university in question. Quick way would involve running SET foreign_key_checks=0 before the DELETE command, and setting the parameter back to 1 after the DELETE is done. If your foreign key was FORMULATED with ON DELETE CASCADE, the data in dependent tables will be removed automatically.

What it means is that so of the data that you’re trying to delete is still alive in another table. Like if you have a table for universities and a table for students, which contains the ID of the university they go to, running a delete on a university table will fail if the students table still contains people enrolled at that university. Proper way to do it would be to delete the offending data first, and then delete the university in question. Quick way would involve running SET foreign_key_checks=0 before the DELETE command, and setting the parameter back to 1 after the DELETE is done. If your foreign key was formulated with ON DELETE CASCADE, the data in dependent tables will be removed automatically.

MAKES the MYSQL engine REFUSE UPDATE and DELETE commands where the WHERE clause is not present.

Makes the MySQL engine refuse UPDATE and DELETE commands where the WHERE clause is not present.

SELECT LAST_INSERT_ID() will RETURN the last value ASSIGNED by the auto_increment function. NOTE that you don’t have to SPECIFY the table NAME.

SELECT LAST_INSERT_ID() will return the last value assigned by the auto_increment function. Note that you don’t have to specify the table name.

It’s equivalent to saying SELECT user_name, user_isp FROM users LEFT JOIN isps WHERE users.user_id=isps.user_id

It’s equivalent to saying SELECT user_name, user_isp FROM users LEFT JOIN isps WHERE users.user_id=isps.user_id

SELECT user_name FROM USERS WHERE ISNULL(user_phonenumber);

SELECT user_name FROM users WHERE ISNULL(user_phonenumber);

SELECT team_name FROM TEAMS WHERE team_won IN (2, 4, 6, 8)

SELECT team_name FROM teams WHERE team_won IN (2, 4, 6, 8)

SELECT SQL_CALC_FOUND_ROWS page_title FROM web_pages LIMIT 1,10; SELECT FOUND_ROWS(); The SECOND query (not that COUNT() is never used) will TELL you how many RESULTS there’re total, so you can display a PHRASE "Found 13,450,600 results, displaying 1-10". Note that FOUND_ROWS does not pay attention to the LIMITS you specified and always returns the total number of rows affected by query.

SELECT SQL_CALC_FOUND_ROWS page_title FROM web_pages LIMIT 1,10; SELECT FOUND_ROWS(); The second query (not that COUNT() is never used) will tell you how many results there’re total, so you can display a phrase "Found 13,450,600 results, displaying 1-10". Note that FOUND_ROWS does not pay attention to the LIMITs you specified and always returns the total number of rows affected by query.

SELECT book_title FROM BOOKS LIMIT 25, 100. The FIRST number in LIMIT is the OFFSET, the second is the number.

SELECT book_title FROM books LIMIT 25, 100. The first number in LIMIT is the offset, the second is the number.

USE DISTINCT in the query, such as SELECT DISTINCT user_firstname FROM users; You can also ask for a number of distinct values by SAYING SELECT COUNT (DISTINCT user_firstname) FROM users;

Use DISTINCT in the query, such as SELECT DISTINCT user_firstname FROM users; You can also ask for a number of distinct values by saying SELECT COUNT (DISTINCT user_firstname) FROM users;

SELECT COUNT (user_id) FROM USERS WOULD only return the NUMBER of user_id’s.

SELECT COUNT (user_id) FROM users would only return the number of user_id’s.

If you look at the large variety of SQL commands, they can be divided into three large subgroups. DATA Definition Language deals with database schemas and DESCRIPTIONS of how the data should reside in the database, therefore language statements like CREATE TABLE or ALTER TABLE belong to DDL. DML deals with data manipulation, and therefore includes most common SQL statements such SELECT, INSERT, etc. Data Control Language includes commands such as GRANT, and mostly concerns with rights, PERMISSIONS and other controls of the database system.

If you look at the large variety of SQL commands, they can be divided into three large subgroups. Data Definition Language deals with database schemas and descriptions of how the data should reside in the database, therefore language statements like CREATE TABLE or ALTER TABLE belong to DDL. DML deals with data manipulation, and therefore includes most common SQL statements such SELECT, INSERT, etc. Data Control Language includes commands such as GRANT, and mostly concerns with rights, permissions and other controls of the database system.

MySQL (pronounced "my ESS cue el") is an OPEN source relational database management system (RDBMS) that uses STRUCTURED QUERY Language (SQL), the most popular language for adding, accessing, and processing data in a database. Because it is open source, anyone can download MySQL and tailor it to their needs in accordance with the general public license. MySQL is noted mainly for its speed, reliability, and flexibility.

MySQL (pronounced "my ess cue el") is an open source relational database management system (RDBMS) that uses Structured Query Language (SQL), the most popular language for adding, accessing, and processing data in a database. Because it is open source, anyone can download MySQL and tailor it to their needs in accordance with the general public license. MySQL is noted mainly for its speed, reliability, and flexibility.