マテリアライズドビューは一般的なVIEWと異なり、データをVIEWの中で実体化する為、VIEWの様に実行される度にデータを定義されているテーブルから呼び出す必要がありません。その為、複雑なSQL処理で且つ更新頻度が低いデータをマテリアライズドビューにしておくことで問題となる重い処理を高速化して安定したサービスを提供する事が可能になります。Oracleデータベースを中心として古くからある技術ですが、レポート系のサービス等では今でも多く活用されています。
PostgreSQL
POC=# select p12_001,p12_002,
ST_X(ST_Centroid(ST_Transform(geom, 4326))) AS long,
ST_Y(ST_Centroid(ST_Transform(geom, 4326))) AS lat from "p12a-14_13" where p12_001 >=10030 order by p12_001 asc limit 10;
p12_001 | p12_002 | long | lat
---------+--------------------------------+--------------------+--------------------
10030 | 国立能楽堂で上演される能・狂言 | 139.7082099985863 | 35.68040399787879
10031 | 三鷹の森ジブリ美術館 | 139.57043200076905 | 35.696237997579054
10032 | 三原山溶岩群 | 139.38170530629864 | 34.73785569987695
10033 | 御蔵島のイルカ | 139.5944977029823 | 33.898130001041196
10034 | 南島(みなみじま) | 142.1754604184242 | 27.03785670484675
10035 | 小笠原のクジラ | 142.18552523057625 | 27.101061872628367
10036 | 小笠原の見送り | 142.1966357837792 | 27.094949847766927
(7 rows)
POC=# CREATE MATERIALIZED VIEW MV_LIST_TOKYO_KANKO AS
select p12_001,p12_002,
ST_X(ST_Centroid(ST_Transform(geom, 4326))) AS long,
ST_Y(ST_Centroid(ST_Transform(geom, 4326))) AS lat from "p12a-14_13" where p12_001 >=10030 order by p12_001 asc limit 10;
SELECT 7
POC=# select * from MV_LIST_TOKYO_KANKO;
p12_001 | p12_002 | long | lat
---------+--------------------------------+--------------------+--------------------
10030 | 国立能楽堂で上演される能・狂言 | 139.7082099985863 | 35.68040399787879
10031 | 三鷹の森ジブリ美術館 | 139.57043200076905 | 35.696237997579054
10032 | 三原山溶岩群 | 139.38170530629864 | 34.73785569987695
10033 | 御蔵島のイルカ | 139.5944977029823 | 33.898130001041196
10034 | 南島(みなみじま) | 142.1754604184242 | 27.03785670484675
10035 | 小笠原のクジラ | 142.18552523057625 | 27.101061872628367
10036 | 小笠原の見送り | 142.1966357837792 | 27.094949847766927
(7 rows)
POC=# UPDATE "p12a-14_13" SET p12_002 = '南島' where p12_001 = 10034;
UPDATE 1
POC=# select * from MV_LIST_TOKYO_KANKO;
p12_001 | p12_002 | long | lat
---------+--------------------------------+--------------------+--------------------
10030 | 国立能楽堂で上演される能・狂言 | 139.7082099985863 | 35.68040399787879
10031 | 三鷹の森ジブリ美術館 | 139.57043200076905 | 35.696237997579054
10032 | 三原山溶岩群 | 139.38170530629864 | 34.73785569987695
10033 | 御蔵島のイルカ | 139.5944977029823 | 33.898130001041196
10034 | 南島(みなみじま) | 142.1754604184242 | 27.03785670484675
10035 | 小笠原のクジラ | 142.18552523057625 | 27.101061872628367
10036 | 小笠原の見送り | 142.1966357837792 | 27.094949847766927
(7 rows)
POC=# REFRESH MATERIALIZED VIEW MV_LIST_TOKYO_KANKO;
REFRESH MATERIALIZED VIEW
POC=# select * from MV_LIST_TOKYO_KANKO;
p12_001 | p12_002 | long | lat
---------+--------------------------------+--------------------+--------------------
10030 | 国立能楽堂で上演される能・狂言 | 139.7082099985863 | 35.68040399787879
10031 | 三鷹の森ジブリ美術館 | 139.57043200076905 | 35.696237997579054
10032 | 三原山溶岩群 | 139.38170530629864 | 34.73785569987695
10033 | 御蔵島のイルカ | 139.5944977029823 | 33.898130001041196
10034 | 南島 | 142.1754604184242 | 27.03785670484675
10035 | 小笠原のクジラ | 142.18552523057625 | 27.101061872628367
10036 | 小笠原の見送り | 142.1966357837792 | 27.094949847766927
(7 rows)
POC=#
REFRESH
CONCURRENTLYは、リフレッシュ中にもアクセス可能にするオプション。
CONCURRENTLYは早朝にリフレッシュする場合は不要 (CONCURRENTLYにはPKやUnique Keyが必要な為）
≒ MVにインデックスを付与する事が出来るので、インデックスを付けて参照処理を高速にする事が可能です。
REFRESH MATERIALIZED VIEW CONCURRENTLY <MATERIALIZED VIEW名>;
or
REFRESH MATERIALIZED VIEW <MATERIALIZED VIEW名>;※ MVのリフレッシュレスポンス（基本的にはMV作成程度の時間がかかるります。）
MATERIALIZED VIEWの削除はテーブルのDROP方法と同様です。
DROP MATERIALIZED VIEW <MATERIALIZED VIEW名>;
MySQL
MySQLで疑似的なマテリアライズド・ビュー作成
MySQLにはOracleやPostgreSQLの様なマテリアライズド・ビューは実装されてません。
その為、トリガーで対応したり、ワークテーブルを作成しておいて、
定期的にデータを入れ替えるような処理で対応する必要があります。
過去の経験では、デイリー、ウイークリーランキングを作成する為に、
以下のようにMySQLのEVENT SCHEDULE機能とREPLACE 構文を利用して変更されたデータを
定期的に入れ替える処理を行ないマテリアライズド・ビューの代わりに利用していました。
メモ：EVENTの代わりに、LinuxのcronやWindows Task Schedulerでも良いかと思います。
イベントを作成してスケジュールします。
このイベントは、イベントスケジューラが有効になっていないかぎり実行されません。
【検証用にテーブルの作成】
ここでは、City_MasterがオリジナルでCity_SnapShotはSNAPコピーとしています。
オリジナルのデータはMySQLのオフィシャルサイトからダウンロードしたWorldデータベースの
Cityテーブルのデータを利用しています。
root@localhost [world2]> CREATE TABLE `City_Master` (
-> `ID` int(11) NOT NULL AUTO_INCREMENT,
-> `Name` char(35) NOT NULL DEFAULT '',
-> `CountryCode` char(3) NOT NULL DEFAULT '',
-> `District` char(20) NOT NULL DEFAULT '',
-> `Population` int(11) NOT NULL DEFAULT '0',
-> `test` varchar(255) DEFAULT NULL,
-> PRIMARY KEY (`ID`),
-> KEY `idx_CountryCode` (`CountryCode`),
-> KEY `idx_City2_Covering` (`ID`,`Name`)
-> ) ENGINE=InnoDB AUTO_INCREMENT=4080 DEFAULT CHARSET=utf8mb4;
Query OK, 0 rows affected (0.08 sec)
root@localhost [world2]> insert into City_Master select * from City;
Query OK, 4079 rows affected (0.15 sec)
Records: 4079 Duplicates: 0 Warnings: 0
root@localhost [world2]> CREATE TABLE `City_SnapShot` (
-> `ID` int(11) NOT NULL AUTO_INCREMENT,
-> `Name` char(35) NOT NULL DEFAULT '',
-> `CountryCode` char(3) NOT NULL DEFAULT '',
-> `District` char(20) NOT NULL DEFAULT '',
-> `Population` int(11) NOT NULL DEFAULT '0',
-> `test` varchar(255) DEFAULT NULL,
-> PRIMARY KEY (`ID`),
-> KEY `idx_CountryCode` (`CountryCode`),
-> KEY `idx_City2_Covering` (`ID`,`Name`)
-> ) ENGINE=InnoDB AUTO_INCREMENT=4080 DEFAULT CHARSET=utf8mb4;
Query OK, 0 rows affected (0.02 sec)
root@localhost [world2]>
root@localhost [world2]> REPLACE INTO City_SnapShot select ID,Name,CountryCode,District,Population,test from City_Master;
Query OK, 4079 rows affected (0.19 sec)
Records: 4079 Duplicates: 0 Warnings: 0
root@localhost [world2]> select * from City_Master where ID = 100;
+-----+---------+-------------+------------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+-----+---------+-------------+------------+------------+------+
| 100 | Paraná | ARG | Entre Rios | 207041 | NULL |
+-----+---------+-------------+------------+------------+------+
1 row in set (0.00 sec)
root@localhost [world2]> select * from City_SnapShot where ID = 100;
+-----+---------+-------------+------------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+-----+---------+-------------+------------+------------+------+
| 100 | Paraná | ARG | Entre Rios | 207041 | NULL |
+-----+---------+-------------+------------+------------+------+
1 row in set (0.00 sec)ここでは、マスターデータのみデータを変更してみます。(207041->207045)
REPLACEコマンドでSnapShotテーブルへ変更を反映してみます。
メモ：PKが同じであれば、データを問題無くリプレースするかどうかの動作確認。
root@localhost [world2]> update City_Master set Population = 207045 where ID = 100;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
root@localhost [world2]> select * from City_Master where ID = 100;
+-----+---------+-------------+------------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+-----+---------+-------------+------------+------------+------+
| 100 | Paraná | ARG | Entre Rios | 207045 | NULL |
+-----+---------+-------------+------------+------------+------+
1 row in set (0.00 sec)
root@localhost [world2]> select * from City_SnapShot where ID = 100;
+-----+---------+-------------+------------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+-----+---------+-------------+------------+------------+------+
| 100 | Paraná | ARG | Entre Rios | 207041 | NULL |
+-----+---------+-------------+------------+------------+------+
1 row in set (0.00 sec)
root@localhost [world2]> REPLACE INTO City_SnapShot select ID,Name,CountryCode,District,Population,test from City_Master;
Query OK, 4080 rows affected (0.10 sec)
Records: 4079 Duplicates: 1 Warnings: 0
root@localhost [world2]> select * from City_Master where ID = 100;
+-----+---------+-------------+------------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+-----+---------+-------------+------------+------------+------+
| 100 | Paraná | ARG | Entre Rios | 207045 | NULL |
+-----+---------+-------------+------------+------------+------+
1 row in set (0.01 sec)
root@localhost [world2]> select * from City_SnapShot where ID = 100;
+-----+---------+-------------+------------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+-----+---------+-------------+------------+------------+------+
| 100 | Paraná | ARG | Entre Rios | 207045 | NULL |
+-----+---------+-------------+------------+------------+------+
1 row in set (0.00 sec)
root@localhost [world2]> ここから、EVENTを有効にして定期的にデータが自動反映されるスケジュールを設定します。
■ オプションファイルへ追加 (event-scheduler=ON)
オプションファイルへの設定変更が反映されているかどうか確認。
メモ：SETコマンドで、動的にも設定可能。
event_schedulerが実行されている事を確認したら、EVENTを作成しスケジュールを設定します。
root@localhost [world2]> show variables like 'event%';
+-----------------+-------+
| Variable_name | Value |
+-----------------+-------+
| event_scheduler | ON |
+-----------------+-------+
1 row in set (0.00 sec)
root@localhost [world2]> show processlist;
+----+-----------------+-----------+--------+---------+------+------------------------+------------------+
| Id | User | Host | db | Command | Time | State | Info |
+----+-----------------+-----------+--------+---------+------+------------------------+------------------+
| 1 | event_scheduler | localhost | NULL | Daemon | 53 | Waiting on empty queue | NULL |
| 4 | root | localhost | world2 | Query | 0 | starting | show processlist |
+----+-----------------+-----------+--------+---------+------+------------------------+------------------+
2 rows in set (0.01 sec)
root@localhost [world2]>
root@localhost [world2]> CREATE EVENT SNAP_SHOT_VIEW_City_Master_City_SnapShot
-> ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 1 HOUR
-> DO
-> REPLACE INTO City_SnapShot select ID,Name,CountryCode,District,Population,test from City_Master;
Query OK, 0 rows affected (0.00 sec)
root@localhost [world2]> show events;
+--------+------------------------------------------+----------------+-----------+----------+---------------------+----------------+----------------+--------+------+---------+------------+----------------------+----------------------+--------------------+
| Db | Name | Definer | Time zone | Type | Execute at | Interval value | Interval field | Starts | Ends | Status | Originator | character_set_client | collation_connection | Database Collation |
+--------+------------------------------------------+----------------+-----------+----------+---------------------+----------------+----------------+--------+------+---------+------------+----------------------+----------------------+--------------------+
| world2 | SNAP_SHOT_VIEW_City_Master_City_SnapShot | root@localhost | SYSTEM | ONE TIME | 2016-06-10 15:23:01 | NULL | NULL | NULL | NULL | ENABLED | 1 | utf8 | utf8_general_ci | utf8mb4_general_ci |
+--------+------------------------------------------+----------------+-----------+----------+---------------------+----------------+----------------+--------+------+---------+------------+----------------------+----------------------+--------------------+
1 row in set (0.00 sec)
root@localhost [world2]> SELECT * FROM information_schema.EVENTS\G
*************************** 1. row ***************************
EVENT_CATALOG: def
EVENT_SCHEMA: world2
EVENT_NAME: SNAP_SHOT_VIEW_City_Master_City_SnapShot
DEFINER: root@localhost
TIME_ZONE: SYSTEM
EVENT_BODY: SQL
EVENT_DEFINITION: REPLACE INTO City_SnapShot select ID,Name,CountryCode,District,Population,test from City_Master
EVENT_TYPE: ONE TIME
EXECUTE_AT: 2016-06-10 15:23:01
INTERVAL_VALUE: NULL
INTERVAL_FIELD: NULL
SQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
STARTS: NULL
ENDS: NULL
STATUS: ENABLED
ON_COMPLETION: NOT PRESERVE
CREATED: 2016-06-10 14:23:01
LAST_ALTERED: 2016-06-10 14:23:01
LAST_EXECUTED: NULL
EVENT_COMMENT:
ORIGINATOR: 1
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
DATABASE_COLLATION: utf8mb4_general_ci
1 row in set (0.00 sec)
root@localhost [world2]> イベントを設定し終わったので、データを変更すれば、
次回のスケジュール（2016-06-10 15:23:01）にはデータが変更される事になります。
データを一件変更してみます。
root@localhost [world2]> select * from City_Master where ID = 1;
+----+-------+-------------+----------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+----+-------+-------------+----------+------------+------+
| 1 | Kabul | AFG | Kabol | 1780000 | NULL |
+----+-------+-------------+----------+------------+------+
1 row in set (0.00 sec)
root@localhost [world2]> select * from City_SnapShot where ID = 1;
+----+-------+-------------+----------+------------+------+
| ID | Name | CountryCode | District | Population | test |
+----+-------+-------------+----------+------------+------+
| 1 | Kabul | AFG | Kabol | 1780000 | NULL |
+----+-------+-------------+----------+------------+------+
1 row in set (0.00 sec)
root@localhost [world2]> update City_Master set Population = 1780001 where ID = 1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
2016-06-10 15:23:01にEVENTが実行されたので、
SnapShot側のテーブルのデータも変更されている事が確認出来ます。
root@localhost [world2]> select *,now() from City_Master where ID = 1;
+----+-------+-------------+----------+------------+------+---------------------+
| ID | Name | CountryCode | District | Population | test | now() |
+----+-------+-------------+----------+------------+------+---------------------+
| 1 | Kabul | AFG | Kabol | 1780001 | NULL | 2016-06-10 14:25:30 |
+----+-------+-------------+----------+------------+------+---------------------+
1 row in set (0.00 sec)
root@localhost [world2]> select *,now() from City_SnapShot where ID = 1;
+----+-------+-------------+----------+------------+------+---------------------+
| ID | Name | CountryCode | District | Population | test | now() |
+----+-------+-------------+----------+------------+------+---------------------+
| 1 | Kabul | AFG | Kabol | 1780000 | NULL | 2016-06-10 14:25:36 |
+----+-------+-------------+----------+------------+------+---------------------+
1 row in set (0.00 sec)
root@localhost [world2]>
root@localhost [world2]> select *,now() from City_SnapShot where ID = 1;
+----+-------+-------------+----------+------------+------+---------------------+
| ID | Name | CountryCode | District | Population | test | now() |
+----+-------+-------------+----------+------------+------+---------------------+
| 1 | Kabul | AFG | Kabol | 1780001 | NULL | 2016-06-10 15:25:16 |
+----+-------+-------------+----------+------------+------+---------------------+
1 row in set (0.00 sec)
root@localhost [world2]>
【集計表】
まずは、JPNの人口を合計したテーブルを作成してデータを入力しておく。
メモ：実際の人口は1億2000万を超えています。
root@localhost [world2]> select CountryCode,SUM(Population) from City_Master where CountryCode='JPN' group by CountryCode;
+-------------+-----------------+
| CountryCode | SUM(Population) |
+-------------+-----------------+
| JPN | 77965107 |
+-------------+-----------------+
root@localhost [world2]> create table City_Summary (
-> ID int(11) NOT NULL,
-> CountryCode char(3) NOT NULL DEFAULT '',
-> Population int(11) NOT NULL DEFAULT '0',
-> PRIMARY KEY (`ID`)
-> ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
Query OK, 0 rows affected (0.02 sec)
root@localhost [world2]> REPLACE INTO City_Summary select 1,CountryCode,SUM(Population) from City_Master where CountryCode='JPN' group by CountryCode;
Query OK, 1 row affected (0.01 sec)
Records: 1 Duplicates: 0 Warnings: 0
root@localhost [world2]> select * from City_Summary;
+----+-------------+------------+
| ID | CountryCode | Population |
+----+-------------+------------+
| 1 | JPN | 77965107 |
+----+-------------+------------+
1 row in set (0.00 sec)
root@localhost [world2]>
東京の人口を10名増やして、EVENTを作成してスケジュールを設定しデータが反映されるか確認してみます。
root@localhost [world2]> update City_Master set Population = 7980240 where Name = 'tokyo';
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0
root@localhost [world2]> select * from City_Summary;
+----+-------------+------------+
| ID | CountryCode | Population |
+----+-------------+------------+
| 1 | JPN | 77965107 |
+----+-------------+------------+
1 row in set (0.00 sec)
root@localhost [world2]> CREATE EVENT SNAP_SHOT_VIEW_City_Master_City_Summary
-> ON SCHEDULE AT CURRENT_TIMESTAMP + INTERVAL 10 MINUTE
-> DO
-> REPLACE INTO City_Summary select 1,CountryCode,SUM(Population) from City_Master where CountryCode='JPN' group by CountryCode;
Query OK, 0 rows affected (0.00 sec)
root@localhost [world2]>
root@localhost [world2]> SELECT * FROM information_schema.EVENTS
-> where EVENT_NAME = 'SNAP_SHOT_VIEW_City_Master_City_Summary'\G
*************************** 1. row ***************************
EVENT_CATALOG: def
EVENT_SCHEMA: world2
EVENT_NAME: SNAP_SHOT_VIEW_City_Master_City_Summary
DEFINER: root@localhost
TIME_ZONE: SYSTEM
EVENT_BODY: SQL
EVENT_DEFINITION: REPLACE INTO City_Summary select 1,CountryCode,SUM(Population) from City_Master where CountryCode='JPN' group by CountryCode
EVENT_TYPE: ONE TIME
EXECUTE_AT: 2016-06-10 15:07:09
INTERVAL_VALUE: NULL
INTERVAL_FIELD: NULL
SQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
STARTS: NULL
ENDS: NULL
STATUS: ENABLED
ON_COMPLETION: NOT PRESERVE
CREATED: 2016-06-10 14:57:09
LAST_ALTERED: 2016-06-10 14:57:09
LAST_EXECUTED: NULL
EVENT_COMMENT:
ORIGINATOR: 1
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
DATABASE_COLLATION: utf8mb4_general_ci
1 row in set (0.01 sec)
root@localhost [world2]> 設定時間に確認してみると、集計データが反映されている事が確認出来ました。
root@localhost [world2]> select *,now() from City_Summary;
+----+-------------+------------+---------------------+
| ID | CountryCode | Population | now() |
+----+-------------+------------+---------------------+
| 1 | JPN | 77965107 | 2016-06-10 14:59:26 |
+----+-------------+------------+---------------------+
1 row in set (0.00 sec)
root@localhost [world2]> select *,now() from City_Summary;
+----+-------------+------------+---------------------+
| ID | CountryCode | Population | now() |
+----+-------------+------------+---------------------+
| 1 | JPN | 77965117 | 2016-06-10 15:07:31 |
+----+-------------+------------+---------------------+
1 row in set (0.00 sec)
root@localhost [world2]>
上記の例は、1回のみ実行する方法でしたが、
一定間隔で,継続して定期的に実行するには、以下の様にEVENTを作ると良いです。
root@localhost [world2]> CREATE EVENT SNAP_SHOT_VIEW_City_Master_City_Summary
-> ON SCHEDULE
-> EVERY 10 MINUTE
-> COMMENT 'サマリーテーブルを10分毎に更新します'
-> DO
-> REPLACE INTO City_Summary select 1,CountryCode,SUM(Population) from City_Master where CountryCode='JPN' group by CountryCode;
Query OK, 0 rows affected (0.00 sec)
root@localhost [world2]> SELECT * FROM information_schema.EVENTS\G
*************************** 1. row ***************************
EVENT_CATALOG: def
EVENT_SCHEMA: world2
EVENT_NAME: SNAP_SHOT_VIEW_City_Master_City_Summary
DEFINER: root@localhost
TIME_ZONE: SYSTEM
EVENT_BODY: SQL
EVENT_DEFINITION: REPLACE INTO City_Summary select 1,CountryCode,SUM(Population) from City_Master where CountryCode='JPN' group by CountryCode
EVENT_TYPE: RECURRING
EXECUTE_AT: NULL
INTERVAL_VALUE: 10
INTERVAL_FIELD: MINUTE
SQL_MODE: ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
STARTS: 2016-06-10 15:46:29
ENDS: NULL
STATUS: ENABLED
ON_COMPLETION: NOT PRESERVE
CREATED: 2016-06-10 15:46:29
LAST_ALTERED: 2016-06-10 15:46:29
LAST_EXECUTED: 2016-06-10 15:46:29
EVENT_COMMENT: サマリーテーブルを10分毎に更新します
ORIGINATOR: 1
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
DATABASE_COLLATION: utf8mb4_general_ci
1 row in set (0.00 sec)
root@localhost [world2]>
OracleやPostgreSQLの様なマテリアライズド・ビュー程の柔軟性やパフォーマンスは無いですが、
こんな対応方法もあるかと思いますので、使えそうでしたら是非試してみて下さい。
メモ： イベントの削除
DROP EVENT イベント名;参考)
13.2.8 REPLACE 構文
https://dev.mysql.com/doc/refman/5.6/ja/replace.html
13.2.5.3 INSERT … ON DUPLICATE KEY UPDATE 構文
https://dev.mysql.com/doc/refman/5.6/ja/insert-on-duplicate.html
13.1.11 CREATE EVENT 構文
https://dev.mysql.com/doc/refman/5.6/ja/create-event.html