In this post, I am sharing a simple solution to move your InnoDB table from one database to another database in MySQL.

Before a few days ago, one of my team members was looking for this solution, and I found that many of Database Administrators do not know about this simple solution.
The solution is, we have to just rename the table name by specifying a database name.

The MySQL InnoDB engine has two types of tablespaces, one is a shared table space and second is an individual tablespace for each table.
This solution works for both the types of tablespaces.

Important Note: ibdata1 file or all .ibd file should be in one MySQL Data Directory at the same location.

After this demonstration, you can visit InnoDB Tablespace related articles.

Create TWO Sample Databases:

CREATE DATABASE ABC;
CREATE DATABASE XYZ;

Create a sample table in database ABC:

USE ABC;

CREATE TABLE tbl_Students
(
	RNO INT 
	,StudName VARCHAR(20)
);

INSERT INTO tbl_Students
VALUES 
(1,'Anvesh'),(2,'Neevan')
,(3,'Jeeny'),(4,'Roy');

Simplest way to move tbl_Students from database ABC to XYZ:

RENAME TABLE ABC.tbl_Students TO XYZ.tbl_Students;

Check tbl_Students in XYZ database:

USE XYZ;

SELECT *FROM tbl_Students;
+------+----------+
| RNO  | StudName |
+------+----------+
|    1 | Anvesh   |
|    2 | Neevan   |
|    3 | Jeeny    |
|    4 | Roy      |
+------+----------+

MySQL: Why InnoDB Engine stores all databases in one file (ibdata1)?

MySQL: The Truth about InnoDB File Per Table Tablespaces

MySQL InnoDB Engine Table Compression, which reduces the size of database size, reduces the CPU I/O and improve overall throughput time.

The compressed data requires the small size of pages, compare to uncompressed data.
MySQL implements compression with the help of the well-known zlib library, which implements the LZ77 compression algorithm.

This compression algorithm is mature, robust, and efficient in both CPU utilization and in a reduction of data size.

Because of compressed data, processors and cache memories increases the speed of execution.
Internally buffer pool fetches the compressed data, uncompressed that data, perform the operation and again write compressed data into Disk.

The default uncompressed size of InnoDB data pages is 16KB.

If innodb_file_per_table variable enable, only we can create compressed table.

For InnoDB system tablespace, we cannot create compressed table because the single InnoDB ibdata1 file also contains other metadata information which we cannot compress.

You can access below articles for more details on InnoDB data files.

MySQL: Why InnoDB Engine stores all databases in one file (ibdata1)?

MySQL: The Truth about InnoDB File Per Table Tablespaces

Mostly, we should enable compression for a read-intensive type of application where RAM frequently uses data.
The default uncompressed size of InnoDB data pages is 16KB and Depending on the combination of option values, MySQL uses a page size of 1KB, 2KB, 4KB, 8KB, or 16KB for the tablespace data file (.ibd file).

How to create an InnoDB Compressed Table?
First In my.cnf or my.ini, innodb_file_per_table required to enable and innodb_file_format must be set to Barracuda.

SET GLOBAL innodb_file_per_table=1;
SET GLOBAL innodb_file_format=Barracuda;

We can create a table with an ROW_FORMAT=COMPRESSED option, which set compressed value half of the innodb_page_size variable.
Explicitly, we can also set a KEY_BLOCK_SIZE value to give a hint.
Here, You can check the size of innodb_page_size. (default 16KB)

SHOW VARIABLES LIKE 'innodb_page_size';

Create Sample InnoDB Compress Table (Set to 8KB):

CREATE TABLE tbl_CompressedTable
(
	CID INT PRIMARY KEY
	,CName VARCHAR(50)
)
ROW_FORMAT=COMPRESSED
KEY_BLOCK_SIZE=8;

Don’t you think so that finding Long Running Queries are a very common requirement for a Database Administrator? ‘

Yes, Database Administrators are always looking for a list of Long Running Queries.

In this post, I am sharing scripts to find Long Running Queries or Transactions of MySQL Database Server.

MySQL DBA can use this script to take necessary steps against the bad and long running queries which increase the overall performance of MySQL Database Server.

In below script, I set 59 seconds internal to find long running query since last 59 seconds.
As per your requirement, you can change this value.

Here, You can also visit few related articles.

MySQL: How to Log General and Long Running Queries into Log Table

MySQL: Using SQL Query Profiler finds total execution time and CPU information of the Queries

Script without using Performance_schema:

SELECT 
	trx.trx_id
	,trx.trx_started
	,trx.trx_mysql_thread_id
FROM INFORMATION_SCHEMA.INNODB_TRX AS trx
INNER JOIN INFORMATION_SCHEMA.PROCESSLIST AS pl 
	ON trx.trx_mysql_thread_id = pl.id
WHERE trx.trx_started < CURRENT_TIMESTAMP - INTERVAL 59 SECOND
  AND pl.user <> 'system_user';

Script using Performance_schema:

SELECT 
	pl.id 'PROCESS ID'
	,trx.trx_started
	,esh.event_name 'EVENT NAME'
	,esh.sql_text 'SQL'
FROM information_schema.innodb_trx AS trx
INNER JOIN information_schema.processlist pl 
	ON trx.trx_mysql_thread_id = pl.id
INNER JOIN performance_schema.threads th 
	ON th.processlist_id = trx.trx_mysql_thread_id
INNER JOIN performance_schema.events_statements_history esh 
	ON esh.thread_id = th.thread_id
WHERE trx.trx_started < CURRENT_TIME - INTERVAL 59 SECOND
  AND pl.user <> 'system_user'
ORDER BY esh.EVENT_ID;

MySQL also supported ARCHIVE Storage Engine which is basically used for storing large amounts of unindexed DATA.
It does not support any type of Indexes, Foreign keys, Concurrency Control and Transactions.

The performance of ARCHIVE Storage Engine is excellent for storing and supporting billions of data.
For any RDBMS system, Bulk Insertion and other Bulk Operations are common.
To increase the performance of BULK Operation, DBA can disable the indexes, can remove the constraints, can compress the table.

But this all are the default settings of the MySQL ARCHIVE Storage Engine.
When you create an ARCHIVE table, the server creates a table format file in the database directory.

The file begins with the table name and has an .frm extension. The storage engine creates other files, all having names beginning with the table name.
The data file has an extension of .ARZ. And .ARN file may appear during optimization operations.

The ARCHIVE engine also uses zlib lossless data compression, so rows are compressed as they are inserted.
We can use OPTIMIZE TABLE to analyze the table and pack it into a smaller format.

Create a sample table using ARCHIVE Storage Engine:

CREATE TABLE tbl_Students
(
	RNO INT NOT NULL
	,StudName VARCHAR(20) NOT NULL
)ENGINE = ARCHIVE ;

Insert few sample records:

INSERT INTO tbl_Students
VALUES 
(1,'Anvesh'),(2,'Neevan')
,(3,'Jeeny'),(4,'Roy');

Check the result:

SELECT *FROM tbl_Students;
+------+----------+
| RNO  | StudName |
+------+----------+
|    1 | Anvesh   |
|    2 | Neevan   |
|    3 | Jeeny    |
|    4 | Roy      |
+------+----------+

One of the most things that I liked about MySQL RDBMS is, It supported different types of Storage Engine for different types of requirement.

I have also published one related article, How to import and export CSV data in MySQL.

MySQL: Import and Export CSV data with Headers

Additionally, MySQL has a wonderful CSV (Comma Separated Value) storage engine to store table data directly into CSV file.

When you create any table with CSV storage engine, It creates table_name.frm file and table_name.csv file into /../MySQL/Data/Database directory.

You can easily open that table_name.csv file and You can also SELECT that CSV table data using MySQL Query Window.

Few Important Points:

CSV storage engine does not support NULL columns, all columns must be NOT NULL.
CSV storage engine does not support any type of Indexing.
CSV storage engine does not support Table Partitioning.

Create a sample table using CSV Stroage Engine:

CREATE TABLE tbl_Students
(
	RNO INT NOT NULL
	,StudName VARCHAR(20) NOT NULL
)ENGINE = CSV;

Insert few records:

INSERT INTO tbl_Students
VALUES 
(1,'Anvesh'),(2,'Neevan')
,(3,'Jeeny'),(4,'Roy');

Check the result of table and also check .csv file which is created in /../MySQL/Data/Database directory.

SELECT *FROM tbl_Students;
+------+----------+
| RNO  | StudName |
+------+----------+
|    1 | Anvesh   |
|    2 | Neevan   |
|    3 | Jeeny    |
|    4 | Roy      |
+------+----------+

In the previous article, I have shared basic about the Performance Schema of MySQL.

MySQL 5.5: Introduced PERFORMANCE_SCHEMA storage engine to inspect the performance data

In this post, I am sharing basic command and configuration of Performance Schema.

Using below command, You can find performance_schema is enabled or disabled.

SHOW VARIABLES LIKE 'performance_schema';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| performance_schema | ON    |
+--------------------+-------+

It is enabled by default, but in the case of any reason if it is not enabled, open your my.cnf or my.ini file and put below parameter value.

[mysqld]
performance_schema=ON

Now It requires restarting the MySQL service because this server parameter enables at server startup.
Using below query, You can also check MySQL database engine information.

SELECT * 
FROM INFORMATION_SCHEMA.ENGINES;

After enable, You can use this schema:

USE performance_schema;

Find out all tables of the Performance Schema:

SHOW TABLES;

Some of the important tables are:

SELECT * FROM events_waits_current; -- To see what the server is doing at the moment
SELECT * FROM file_instances; --  To get instances of instruments for file I/O operations and their associated files

Performance schema has also few parameter tables like instruments and staging:

The Performance Schema instruments stages, which are steps during the statement-execution process, such as parsing a statement, opening a table, or performing a file sort operation.

Stages correspond to the thread states displayed by SHOW PROCESSLIST or that are visible in the INFORMATION_SCHEMA.PROCESSLIST table. Stages begin and end when state values change.

Performance schema setup_instruments table:

SELECT * FROM setup_instruments 
WHERE NAME RLIKE 'stage/sql/[a-c]';

Example to enable one of parameter:

UPDATE setup_instruments SET ENABLED = 'YES', TIMED = 'YES'
WHERE NAME = 'stage/sql/altering table';

Peformance schema setup_consumers table:

SELECT * FROM setup_consumers 
WHERE NAME LIKE '%stages%';

Example to enable one parameter:

UPDATE setup_consumers SET ENABLED ='YES' 
WHERE NAME = 'events_stages_current';

Before starting to database performance tuning activities, Database Administrator requires different types of statistics like wait events, connection time, instance information, lock tables.

MySQL 5.5 introduced a PERFORMANCE_SCHEMA storage engine to monitor the performance of data and different types of server events.
One performance_schema database is created under the PERFORMANCE_SCHEMA storage engine.

An INFORMATION_SCHEMA focuses on METADATA information, but PERFORMANCE_SCHEMA primary focuses on MySQL Database Performance related Data.

The Performance Schema is also collecting different types of MySQL Server event with the related time information.
It stores all collected information in the table so that we can easily access it.

The Performance Schema events are specific to an instance of MySQL Server and changes are not written to the binary log.

We can set enable or disable PERFORMANCE_SCHEMA storage engine. Once it enables, it collects and monitors the different performance related event stats.

The main advantage of Performance Schema is, it never changes the server behaviour and never disturb to Query Planner for making a Query Execution Plan.

The execution of server proceeds normally even if the Performance Schema fails internally.

Please visit the next article about, How to configure Performance Schema and basic usage of it.

For all the RDBMS, Database Statistics are playing the main role to generate an accurate Query Execution Plan.
A Database Administrator is also very much responsible to make sure that Database Statistics is updated.

MySQL query optimizer is also preparing Query Execution Plan with the help of Statistics Information.
The auto-update Statistics configuration is also very important to keep Statistics updated.

How to enable auto-update Statistics for InnoDB engine?

We can configure innodb_stats_on_metadata variable to enable auto-update Statistics.

When this variable is enabled InnoDB updates statistics when metadata statements such as SHOW TABLE STATUS or SHOW INDEX are run, or when accessing the INFORMATION_SCHEMA.TABLES or INFORMATION_SCHEMA.STATISTICS tables.

Check innodb_stats_on_metadata is ON or OFF:

SHOW VARIABLES LIKE 'innodb_stats_on_metadata';

If innodb_stats_on_metadata is OFF, make it ON:

SET GLOBAL innodb_stats_on_metadata=ON;

When you perform command like SHOW INDEX, Statisitcs will be update.
Accuracy of statistics is depends on MySQL Server Load.

SHOW INDEXES FROM SchemaName.TableName;

You can use below query to check the Index Statistics:

SELECT 
    Table_Schema
    ,Table_Name
    ,Non_Unique
    ,Index_Schema
    ,Seq_In_Index
    ,Column_Name
    ,Collation
    ,Cardinality
    ,Index_Type
FROM information_schema.statistics 
WHERE TABLE_SCHEMA='SchemaName';

Have you ever wished that you do not want to insert any data, but want to execute INSERT command ?

This is looking like a very strange requirement, but this is possible in MySQL.

MySQL has a BLACKHOLE Storage Engine which we can use for the empty or the dummy INSERT on Table.

When we created a BLACKHOLE table, It creates with only .frm table format file and It has no any other file associated with it.

When you execute your INSERT on BLACKHOLE Table, It stores only binary log and It does not store any kind of data.

When we should use BLACKHOLE Storage Engine?

When we require to measure the performance only on the binary logging process. Mostly we require to test binary logging performance for bulk operations.

When we require to find performance bottlenecks not related to disk-storage.

When we require slave-side data validation and filtering, we can create a dummy BLACKHOLE table at the master-side which reduces the overall traffic.

Check the status of BLACKHOLE Engine:

SHOW ENGINES;

Create BLACKHOLE table:

CREATE TABLE tbl_Students
(
    RNO INT NOT NULL
    ,StudName VARCHAR(20) NOT NULL
)ENGINE = BLACKHOLE;

Try to insert few records:

INSERT INTO tbl_Students
VALUES 
(1,'Anvesh'),(2,'Neevan')
,(3,'Jeeny'),(4,'Roy');

Check inserted data, which return Empty Set:

SELECT *FROM tbl_Students;
Empty set (0.00 sec)

In this post, I am sharing one of important and basic article about, How to create a SQL Job or scheduler in the MySQL Database Server.

For scheduling the database tasks are very common exercise for all Database Developers and Database Administrators.

The SQL Agent is available in SQL Server and The PG Agent is available in PostgreSQL.

If you want to schedule your database task in MySQL, You should use default Event Scheduler of MySQL Database Server.

You can define event using CREATE EVENT statement and It requires the EVENT privilege for the schema in which the event is to be created.

It might also require the SUPER privilege.

You can access below full demonstration step by step.

Create a sample table:

CREATE TABLE tbl_Students 
(
	StudID INT 
    ,StudName VARCHAR(50)
);

SET GLOBAL event_scheduler = ON;

SET GLOBAL event_scheduler = ON;

SHOW PROCESSLIST;
-- event_scheduler User is running under command "Daemon"

CREATE EVENT Eve_tbl_Students_Temp_Insert
ON SCHEDULE EVERY 1 MINUTE
DO
  INSERT INTO tbl_Students 
  VALUES (1,'Anvesh');

CREATE EVENT Eve_tbl_Students_Temp_Delete
ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 MINUTE
DO
  DELETE FROM tbl_Students;

ALTER EVENT Eve_tbl_Students_Temp_Insert ON SCHEDULE EVERY 2 MINUTE;

ALTER EVENT Eve_tbl_Students_Temp_Insert DISABLE; 
ALTER EVENT Eve_tbl_Students_Temp_Delete DISABLE;

DROP EVENT Eve_tbl_Students_Temp_Insert;
DROP EVENT Eve_tbl_Students_Temp_Delete;