MySQL Tutorials

Author: learning-zone

mysql-basics.sql

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+
+01. Import ".sql" file from command prompt
+
+mysql > SOURCE C://database.sql;     
+
+02. MySQL Performance Queries
+
+mysql > OPTIMIZE TABLE table_name;
+mysql > SHOW TABLE STATUS;  //Displays description of the table
+mysql > DESC table_name;
+mysql > SHOW VARIABLES;
+mysql > SHOW STATUS;
+mysql > SHOW GLOBAL STATUS;
+mysql > SHOW TABLES FROM INFORMATION_SCHEMA;
+mysql > EXPLAIN SELECT * FROM table_name
+mysql > SHOW TABLE STATUS FROM database_name;
+mysql > SHOW FULL PROCESSLIST;  //Shows you which threads are running
+mysql > SHOW VARIABLES WHERE Variable_name = 'hostname';  //IP Address of the Mysql Host
+
+03. Indexing
+
+mysql > SHOW INDEX FROM table_name;
+mysql > ALTER TABLE `table_name` ADD INDEX(`column_name`);
+mysql > DROP INDEX index_name ON tbl_name;
+
+04. Table Related Queries
+
+
+mysql > SELECT max(RIGHT(`field_name`,4)) FROM `table_name`;
+mysql > SELECT UCASE(column_name) FROM table_name;  // Converts to upper case
+mysql > SELECT * FROM TABLE ORDER BY ABS(VALUE - $MYVALUE) LIMIT 1 //Select nearest value
+mysql > SELECT sentence, wordcount(sentence) as "Words" from test;
+mysql > SELECT * FROM table_name ORDER BY field_name LIMIT 5 OFFSET 5;  //Useful in pagination
+mysql > SELECT *,  COUNT(field_name)  FROM table_name GROUP BY field_name HAVING ( COUNT(field_name) > 1 ) //Find duplicate entries
+
+mysql > ALTER TABLE table_name AUTO_INCREMENT =1
+mysql > ALTER TABLE `table_name` DROP PRIMARY KEY 
+mysql > ALTER TABLE `table_name` ENGINE = InnoDB
+mysql > ALTER TABLE table_name CHANGE `id` `id` INT( 11 ) NOT NULL AUTO_INCREMENT 
+mysql > ALTER TABLE `table_name` ADD `id` INT NOT NULL AUTO_INCREMENT PRIMARY KEY FIRST ;
+mysql > ALTER TABLE table_name ADD column_name datatype AFTER column_name 
+mysql > ALTER TABLE table_name DROP COLUMN column_name  
+mysql > ALTER TABLE table_name MODIFY column_name datatype
+mysql > ALTER TABLE table_name CHANGE oldname newname datatype
+
+mysql > RENAME TABLE `table_name_old` TO `table_name_new`
+
+mysql > UPDATE mytable SET city = REPLACE(city, 'ï', 'i')   //Update particular character
+mysql > UPDATE swap_test SET x=y, y=@temp where @temp:=x;   //Swaping field value
+mysql > UPDATE table_name SET field_name1=field_name2;      //COPYING
+mysql > UPDATE table_name SET field_name = UPPER(field_name)
+
+mysql > TRUNCATE TABLE table_name;
+mysql > DROP TABLE table_name;
+mysql > 
+
+05. Date and time
+
+mysql > SHOW VARIABLE LIKE '%time_zone%';
+mysql > SELECT NOW(); //Current timestamp
+mysql > SELECT DAYNAME(NOW()); //Current day
+mysql > SELECT SUBTIME('1:30:00', '00:15:00'); //Subtract time
+mysql > SELECT DATE_FORMAT(NOW(), '%W, %D of %M, %Y'); //Date Format 
+mysql > SELECT TIMEDIFF('2007-10-05 12:10:18','2007-10-05 16:14:59') AS length;
+mysql > SELECT * FROM `table_name` WHERE DATE_FORMAT(field_name, "%Y-%m-%d") = '2010-01-01'"
+
+
+06. MySQL Miscellaneous Queries
+
+mysql > SELECT uuid(); //Use to generate unique id 
+mysql > SELECT * FROM `TABLENAME` WHERE `field` REGEXP '^-?[0-9]+$' //Get numeric values 
+mysql > SELECT CONCAT('w3resource','.','com'); //w3resource.com
+mysql > CREATE TABLE table_bit (id SERIAL, a BIT(3), b BIT(8), c BIT(16)); //bit datatype
+mysql > CREATE TABLE table_enum (id SERIAL, status ENUM('Active', 'Deactive')); //Enum datatype
+mysql > SELECT CHAR_LENGTH(field_name) AS Length FROM `table_name`; //Get the length 
+mysql > SELECT * FROM `table_name` WHERE LENGTH(field_name) < 10
+mysql > INSERT INTO table_name (`col1`, `col2`, `col3`, `...`, `coln`) SELECT `col1`, `col2`, `col3`, `...`, `coln` FROM table_name //Copying the previous rows to the next rows
+mysql > SELECT COUNT(DISTINCT column) FROM table;
+mysql > SELECT field_name, LEFT(field_name, 3), RIGHT(field_name, 3), MID(field_name, 2, 3) FROM `table_name`;
+mysql > SELECT CASE WHEN a THEN 'true' ELSE 'false' END AS boolA, CASE WHEN b THEN 'true' ELSE 'false' END AS boolB FROM table_name; //Flow control with CASE
+
+
+ 

mysql-engines.sql

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+/**
+
+InnoDB:    The default storage engine in MySQL 8.0. InnoDB is a transaction-safe (ACID compliant) storage engine for MySQL 
+           that has commit, rollback, and crash-recovery capabilities to protect user data. InnoDB row-level locking 
+           (without escalation to coarser granularity locks) and Oracle-style consistent nonlocking reads increase multi-user 
+           concurrency and performance. InnoDB stores user data in clustered indexes to reduce I/O for common queries based on primary keys. 
+           To maintain data integrity, InnoDB also supports FOREIGN KEY referential-integrity constraints. 
+
+MyISAM:    These tables have a small footprint. Table-level locking limits the performance in read/write workloads, 
+           so it is often used in read-only or read-mostly workloads in Web and data warehousing configurations.
+
+Memory:    Stores all data in RAM, for fast access in environments that require quick lookups of non-critical data. This engine 
+           was formerly known as the HEAP engine. Its use cases are decreasing; InnoDB with its buffer pool memory area provides a 
+           general-purpose and durable way to keep most or all data in memory, and NDBCLUSTER provides fast key-value lookups for huge distributed data sets.
+
+CSV:       Its tables are really text files with comma-separated values. CSV tables let you import or dump data in CSV format, to exchange 
+           data with scripts and applications that read and write that same format. Because CSV tables are not indexed, you typically keep 
+           the data in InnoDB tables during normal operation, and only use CSV tables during the import or export stage.
+
+Archive:   These compact, unindexed tables are intended for storing and retrieving large amounts of seldom-referenced historical, archived, 
+           or security audit information.
+
+Blackhole: The Blackhole storage engine accepts but does not store data, similar to the Unix /dev/null device. Queries always return an empty 
+           set. These tables can be used in replication configurations where DML statements are sent to slave servers, but the master server does not keep its own copy of the data.
+
+NDB:       This clustered database engine is particularly suited for applications that require the highest possible degree 
+           of uptime and availability.
+
+Merge:     Enables a MySQL DBA or developer to logically group a series of identical MyISAM tables and reference them as one object. 
+           Good for VLDB environments such as data warehousing.
+
+Federated: Offers the ability to link separate MySQL servers to create one logical database from many physical servers. Very good for 
+           distributed or data mart environments.
+
+Example:   This engine serves as an example in the MySQL source code that illustrates how to begin writing new storage engines. 
+           It is primarily of interest to developers. The storage engine is a “stub” that does nothing. You can create tables with this engine, but no data can be stored in them or retrieved from them.
+
+
+**/
+
+mysql > SHOW ENGINES\G;
+
+//*************************** 1. row ***************************
+      Engine: PERFORMANCE_SCHEMA
+     Support: YES
+     Comment: Performance Schema
+Transactions: NO
+          XA: NO
+  Savepoints: NO
+*************************** 2. row ***************************
+      Engine: InnoDB
+     Support: DEFAULT
+     Comment: Supports transactions, row-level locking, and foreign keys
+Transactions: YES
+          XA: YES
+  Savepoints: YES
+*************************** 3. row ***************************
+      Engine: MRG_MYISAM
+     Support: YES
+     Comment: Collection of identical MyISAM tables
+Transactions: NO
+          XA: NO
+  Savepoints: NO
+*************************** 4. row ***************************
+      Engine: BLACKHOLE
+     Support: YES
+     Comment: /dev/null storage engine (anything you write to it disappears)
+Transactions: NO
+          XA: NO
+  Savepoints: NO
+*************************** 5. row ***************************
+      Engine: MyISAM
+     Support: YES
+     Comment: MyISAM storage engine
+Transactions: NO
+          XA: NO
+  Savepoints: NO
+...
+**/

stored-routines.sql

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+
+/***
+A stored routine is a set of SQL statements that are stored on the database server and can be used by any client 
+with permission to use them. This provides a number of benefits. 
+
+1. Database operations are normalized so various applications will operate uniformly, even when written in different 
+   languages and operating on different platforms. 
+   
+2. Stored routines are easy to maintain, because they're all in one place rather than distributed among different applications.
+
+3. Traffic is reduced between the client and server, because data is processed on the server.
+
+4. security is enhanced by allowing clients to run with reduced permissions while still being able to perform necessary 
+   database operations. 
+   
+There are also some disadvantages. 
+
+1. Migration to a different server platform can be difficult as stored routines tend to use a lot of platform specific 
+   features and codes. 
+   
+2. stored procedures can be difficult to debug and maintain. 
+
+There are two different kinds of stored routines. 
+
+a) Stored functions return a value, and are used in the context of an expression.
+
+b) Stored procedures are called separately, using the call statement, and may return result sets or set variables. 
+
+***/
+
+
+
+---Example - 01 : Stored Functions
+
+DROP FUNCTION IF EXISTS track_len;
+
+CREATE FUNCTION track_len(seconds INT)
+RETURNS VARCHAR(16) DETERMINISTIC
+    RETURN CONCAT_WS(':', seconds DIV 60, LPAD(seconds MOD 60, 2, '0' ));
+
+SELECT title, track_len(duration) FROM track;
+
+SELECT a.artist AS artist,
+    a.title AS album,
+    t.title AS track,
+    t.track_number AS trackno,
+    track_len(t.duration) AS length
+  FROM track AS t
+  JOIN album AS a
+    ON a.id = t.album_id
+  ORDER BY artist, album, trackno
+;
+
+
+
+---Example - 02 : Stored Procedures
+
+DROP PROCEDURE IF EXISTS list_albums;
+
+DELIMITER //
+CREATE PROCEDURE list_albums ()
+BEGIN
+    SELECT * FROM album;
+END
+//
+
+DELIMITER ;
+CALL list_albums();
+
+
+---Example - 03 : Stored Procedures with parameter
+
+DROP PROCEDURE IF EXISTS list_albums;
+
+DELIMITER //
+CREATE PROCEDURE list_albums (a VARCHAR(255))
+  BEGIN
+    SELECT a.artist AS artist,
+        a.title AS album,
+        t.title AS track,
+        t.track_number AS trackno,
+        track_len(t.duration) AS length
+      FROM track AS t
+      JOIN album AS a
+        ON a.id = t.album_id
+      WHERE a.artist LIKE a
+      ORDER BY artist, album, trackno
+    ;
+  END //
+
+DELIMITER ;
+CALL list_albums('%hendrix%');
+
+
+---Example - 03 : Drop Stored Procedures & Stored Functions
+
+DROP FUNCTION IF EXISTS track_len;
+DROP PROCEDURE IF EXISTS total_duration;

transaction.sql

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+-- Exmaple - 01
+
+CREATE TABLE widgetInventory (
+    id SERIAL,
+    description VARCHAR(255),
+    onhand INTEGER NOT NULL
+);
+
+CREATE TABLE widgetSales (
+    id SERIAL,
+    inv_id INTEGER,
+    quan INTEGER,
+    price INTEGER
+);
+
+INSERT INTO widgetInventory ( description, onhand ) VALUES  ( 'rock', 25 );
+INSERT INTO widgetInventory ( description, onhand ) VALUES  ( 'paper', 25 );
+INSERT INTO widgetInventory ( description, onhand ) VALUES  ( 'scissors', 25 );
+
+
+START TRANSACTION;
+INSERT INTO widgetSales ( inv_id, quan, price ) VALUES ( 1, 5, 500 );
+UPDATE widgetInventory SET onhand = ( onhand - 5 ) WHERE id = 1;
+COMMIT;
+
+SELECT * FROM widgetInventory;
+SELECT * FROM widgetSales;
+
+START TRANSACTION;
+INSERT INTO widgetInventory ( description, onhand ) VALUES ( 'toy', 25 );
+ROLLBACK;
+SELECT * FROM widgetInventory;
+SELECT * FROM widgetSales;
+
+
+---Example - 02 INSERT Query using Transaction
+
+CREATE TABLE test (
+    id SERIAL,
+    data VARCHAR(256)
+);
+
+-- Insert 1,000 times ...
+INSERT INTO test ( data ) VALUES ( 'this is a good sized line of text.' );
+
+
+--- Insert 1000 times using Transaction
+START TRANSACTION;
+
+INSERT INTO test ( data ) VALUES ( 'this is a good sized line of text.' );
+COMMIT;

triggers.sql

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+-- Example - 01: Updating a table with a trigger
+
+
+CREATE TABLE widgetCustomer ( id SERIAL, name VARCHAR(255), last_order_id BIGINT );
+CREATE TABLE widgetSale ( id SERIAL, item_id BIGINT, customer_id BIGINT, quan INT, price DECIMAL(9,2) );
+
+INSERT INTO widgetCustomer (name) VALUES ('Bob');
+INSERT INTO widgetCustomer (name) VALUES ('Sally');
+INSERT INTO widgetCustomer (name) VALUES ('Fred');
+
+SELECT * FROM widgetCustomer;
+
+CREATE TRIGGER newWidgetSale AFTER INSERT ON widgetSale
+    FOR EACH ROW
+    UPDATE widgetCustomer SET last_order_id = NEW.id WHERE id = NEW.customer_id
+;
+
+INSERT INTO widgetSale (item_id, customer_id, quan, price) VALUES (1, 3, 5, 19.95);
+INSERT INTO widgetSale (item_id, customer_id, quan, price) VALUES (2, 2, 3, 14.95);
+INSERT INTO widgetSale (item_id, customer_id, quan, price) VALUES (3, 1, 1, 29.95);
+SELECT * FROM widgetSale;
+SELECT * FROM widgetCustomer;

view.sql

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+---Example - 01 : Creating a View
+
+SELECT id, album_id, title, track_number, duration DIV 60 AS m, duration MOD 60 AS s
+  FROM track;
+
+CREATE VIEW trackView AS
+  SELECT id, album_id, title, track_number, duration DIV 60 AS m, duration MOD 60 AS s
+    FROM track;
+SELECT * FROM trackView;
+
+
+
+---Exmaple - 02 : Joined view
+
+SELECT a.artist AS artist,
+    a.title AS album,
+    t.title AS track,
+    t.track_number AS trackno,
+    t.duration DIV 60 AS m,
+    t.duration MOD 60 AS s
+  FROM track AS t
+  JOIN album AS a
+    ON a.id = t.album_id
+;
+
+
+CREATE VIEW joinedAlbum AS
+  SELECT a.artist AS artist,
+      a.title AS album,
+      t.title AS track,
+      t.track_number AS trackno,
+      t.duration DIV 60 AS m,
+      t.duration MOD 60 AS s
+    FROM track AS t
+    JOIN album AS a
+      ON a.id = t.album_id
+;
+
+SELECT * FROM joinedAlbum;
+SELECT * FROM joinedAlbum WHERE artist = 'Jimi Hendrix';
+
+
+---Example - 03 : Drop View
+
+DROP VIEW IF EXISTS joinedAlbum;