'MySQL' 태그의 글 목록

[MySQL] group_concat 사용 시 순서 지정.

ITWeb/개발일반 2021. 11. 29. 18:28

참고문서)

https://dev.mysql.com/doc/refman/8.0/en/aggregate-functions.html#function_group-concat

group by 를 이용해서 특정 컬럼의 value 를 concat 할 경우 해당 테이블의 특정 컬럼으로 순서를 맞춰 줘야 할 경우가 있습니다.

group_concat 함수 내부에 order by 를 이용해서 적용 하시면 됩니다.

이렇게 하지 않았을 경우 순서에 대해 보장이 된다고 간혹 착각 할 수 있느데 주의 해서 사용하시기 바랍니다.

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[MySQL] HikariCP Connection Pool 관리 예.

ITWeb/개발일반 2021. 8. 9. 08:12

HikariCP 를 사용하고 있는데 Connection Pool 에 대한 반납과 재사용이 원활 하지 않을 때가 있습니다.

Application 내부에서 사용과 반납을 너무 빈번하게 하고 있을 경우 이런 문제가 발생 하는 것 같습니다.

보통은 별 문제 없이 사용을 했으나 이런 문제가 발생 한다면 명시적으로 Close 를 해주고 다시 Connection 을 생성해 주면 문제를 해소 할 수 있습니다.

기억하기 위해 기록 합니다.

    config.setDriverClassName("com.mysql.cj.jdbc.Driver");
    config.setJdbcUrl("jdbc:mysql://....");
    config.setUsername(user);
    config.setPassword(pwd);
    config.setMaximumPoolSize(maxPoolSize);
    config.setMinimumIdle(minimumIdle);
    config.setConnectionTimeout(30000);
    config.setValidationTimeout(10000);
    config.setConnectionTestQuery("SELECT 1");
    config.addDataSourceProperty("autoReconnect", "true");
    config.addDataSourceProperty("serverTimezone", "Asia/Seoul");
    config.addDataSourceProperty("cachePrepStmts", "true");
    config.addDataSourceProperty("prepStmtCacheSize", "250");
    config.addDataSourceProperty("prepStmtCacheSqlLimit", "2048");
    config.addDataSourceProperty("dataSource.useServerPrepStmts", "true");
    config.addDataSourceProperty("characterEncoding","utf8");
    config.addDataSourceProperty("useUnicode","true");
    
    this.ds = new HikariDataSource(config);

getConnection() 은 pool 에서 얻어 옵니다.

getConnection().close() 하면 pool 을 반납 하게 됩니다.

근데 이게 반납과 재사용이 잘 안된다. 그러면 ds.close() 하고 다시 connection 을 생성 합니다. (HikariDataSource ds)

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[Docker] 로컬에 MySQL 설치 합니다.

Cloud&Container/IaC 2021. 7. 14. 19:39

요즘 잘 되어 있는 container 기반으로 구성 하면 되지 않겠습니까?

version: '3.7'

services:
  db:
    image: mysql
    container_name: local-mysql
    command: --default-authentication-plugin=mysql_native_password
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: local
      MYSQL_USER: henry
      MYSQL_PASSWORD: henry
      MYSQL_DATABASE: henry
    volumes:
      - ./data:/var/lib/mysql
    ports:
      - 3306:3306

  adminer:
    image: adminer
    restart: always
    ports:
      - 8888:8888

$ docker-compose up -d

이제 client tool 을 이용해서 접속해 보시면 됩니다. :)

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[MySQL] mysql.user 테이블에 계정 추가하기.

ITWeb/서버관리 2018. 6. 12. 13:21

[MySQL 5.7 에서 User 등록]

INSERT INTO `user` (`Host`, `User`, `Select_priv`, `Insert_priv`, `Update_priv`, `Delete_priv`, `Create_priv`, `Drop_priv`, `Reload_priv`, `Shutdown_priv`, `Process_priv`, `File_priv`, `Grant_priv`, `References_priv`, `Index_priv`, `Alter_priv`, `Show_db_priv`, `Super_priv`, `Create_tmp_table_priv`, `Lock_tables_priv`, `Execute_priv`, `Repl_slave_priv`, `Repl_client_priv`, `Create_view_priv`, `Show_view_priv`, `Create_routine_priv`, `Alter_routine_priv`, `Create_user_priv`, `Event_priv`, `Trigger_priv`, `Create_tablespace_priv`, `ssl_type`, `ssl_cipher`, `x509_issuer`, `x509_subject`, `max_questions`, `max_updates`, `max_connections`, `max_user_connections`, `plugin`, `authentication_string`, `password_expired`, `password_last_changed`, `password_lifetime`, `account_locked`)

VALUES

('%','root','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','','','','',0,0,0,0,'mysql_native_password',password('1234'),'N',NOW(),NULL,'N')

- 아래는 아마도 MySQL 5.6 이하 버전에서 동작 했던 것 같습니다.

SQL 문으로 계정 추가하기 위한 쿼리 입니다.

로컬 개발서버 기준으로 작성 된 것이기 때문에 보안에 문제가 될 수도 있으니 주의 하시기 바랍니다.

grant all 입니다.

mysql> INSERT INTO user

VALUES ('localhost', 'cloumon', password('cloumon'), 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', 'Y', '', '', '', '', 0, 0, 0, 0, '', '', 'N');

mysql> FLUSH PRIVILEGES;

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[MySQL] JSON Type 사용하기

ITWeb/개발일반 2016. 7. 21. 10:12

elasticsearch에서 문서 데이터를 처리 하다 보니 json format을 많이 사용하게 됩니다.

그래서 색인을 위한 데이터중 일부는 mysql 에 json 형태로 저장할 필요가 있는데요. mysql 5.7 부터 data type 으로 json 을 지원하고 있습니다.

참고문서)

https://dev.mysql.com/doc/refman/5.7/en/json.html

https://dev.mysql.com/doc/refman/5.7/en/json-function-reference.html

선언)

CREATE TABLE XXXX (

seq BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,

doc JSON NOT NULL,

PRIMARY KEY (seq)

) ENGINE = InnoDB

CHARACTER SET utf8

COLLATE utf8_general_ci;

등록)

INSERT INTO XXXX(doc) VALUE (?)

조회)

SELECT doc

FROM XXXX

JDBC)

# 등록

PrepareStatement.setObject(1, OBJECT);

# 조회

ResultSet.getObjecrt(1, "doc");

- JDBC 를 통해 DB 에 등록 할 때 value 값에 대한 Object를 Array 인지 Object 인지 확인해서 넣어 주어야 값이 원하는 형태로 저장 됩니다.

Elasticsearch Mapping)

"FIELD_NAME": { "type":"object", "enabled":false }

저작자표시 비영리 변경금지

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[MySQL] root password 리셋하기.

ITWeb/개발일반 2016. 4. 30. 01:30

mysql 설치 후 root 암호가 기억나지 않을 경우 리셋 할때 사용하시면 됩니다.

mysql 데몬을 떠 있으면 중지 하시고 아래 옵션을 주고 실행해 준 후 root 로 접속해서 암호를 다시 변경 하시면 됩니다.

sudo mysqld_safe --skip-grant-tables &

저작자표시 비영리 변경금지

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[Mysql] create database syntax example.

ITWeb/개발일반 2016. 3. 9. 15:30

뭘 이런걸 기록하는지 모르겠지만 나이 먹으면 이런것도 자꾸 까먹습니다.

참고문서)

http://dev.mysql.com/doc/refman/5.7/en/create-database.html

기본 Syntax)

CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
    [create_specification] ...

create_specification:
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name

예제)

mysql> create database 생성할데이터베이스명 default character set utf8 collate utf8_general_ci;

저작자표시 비영리 변경금지

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[MySQL] SQL JOINS 그림 설명.

ITWeb/개발일반 2016. 2. 17. 12:05

RDBMS를 최근 잘 사용 안 했더니 join이 다시 궁금해져서 구글링 했습니다.

이미지로 설명이 잘 나와 있내요. :)

저작자표시 비영리 변경금지

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11.6 Data Type Storage Requirements

ITWeb/개발일반 2014. 3. 7. 17:27

http://dev.mysql.com/doc/refman/5.1/en/storage-requirements.html

11.6 Data Type Storage Requirements

The storage requirements for data vary, according to the storage engine being used for the table in question. Different storage engines use different methods for recording the raw data and different data types. In addition, some engines may compress the information in a given row, either on a column or entire row basis, making calculation of the storage requirements for a given table or column structure.

However, all storage engines must communicate and exchange information on a given row within a table using the same structure, and this information is consistent, irrespective of the storage engine used to write the information to disk.

This sections includes some guideliness and information for the storage requirements for each data type supported by MySQL, including details for the internal format and the sizes used by storage engines that used a fixed size representation for different types. Information is listed by category or storage engine.

The internal representation of a table has a maximum row size of 65,535 bytes, even if the storage engine is capable of supporting larger rows. This figure excludes BLOB or TEXT columns, which contribute only 9 to 12 bytes toward this size. For BLOB and TEXT data, the information is stored internally in a different area of memory than the row buffer. Different storage engines handle the allocation and storage of this data in different ways, according to the method they use for handling the corresponding types. For more information, see Chapter 14, Storage Engines, and Section E.7.4, “Limits on Table Column Count and Row Size”.

Storage Requirements for `InnoDB` Tables

See Section 14.6.3.12.5, “Physical Row Structure” for information about storage requirements for InnoDB tables.

Storage Requirements for `NDBCLUSTER` Tables

Important

For tables using the NDBCLUSTER storage engine, there is the factor of 4-byte alignment to be taken into account when calculating storage requirements. This means that all NDB data storage is done in multiples of 4 bytes. Thus, a column value that would take 15 bytes in a table using a storage engine other than NDB requires 16 bytes in an NDB table. This requirement applies in addition to any other considerations that are discussed in this section. For example, in NDBCLUSTER tables, the TINYINT, SMALLINT, MEDIUMINT, and INTEGER (INT) column types each require 4 bytes storage per record due to the alignment factor.

An exception to this rule is the BIT type, which is not 4-byte aligned. In MySQL Cluster tables, a BIT(M) column takes M bits of storage space. However, if a table definition contains 1 or more BIT columns (up to 32 BIT columns), then NDBCLUSTER reserves 4 bytes (32 bits) per row for these. If a table definition contains more than 32 BIT columns (up to 64 such columns), then NDBCLUSTER reserves 8 bytes (that is, 64 bits) per row.

In addition, while a NULL itself does not require any storage space, NDBCLUSTER reserves 4 bytes per row if the table definition contains any columns defined as NULL, up to 32 NULL columns. (If a MySQL Cluster table is defined with more than 32 NULL columns up to 64 NULL columns, then 8 bytes per row is reserved.)

When calculating storage requirements for MySQL Cluster tables, you must also remember that every table using the NDBCLUSTER storage engine requires a primary key; if no primary key is defined by the user, then a “hidden” primary key will be created by NDB. This hidden primary key consumes 31-35 bytes per table record.

You may find the ndb_size.pl utility to be useful for estimating NDB storage requirements. This Perl script connects to a current MySQL (non-Cluster) database and creates a report on how much space that database would require if it used the NDBCLUSTER storage engine. See Section 17.4.23, “ndb_size.pl — NDBCLUSTER Size Requirement Estimator”, for more information.

Storage Requirements for Numeric Types

Data Type	Storage Required
`TINYINT`	1 byte
`SMALLINT`	2 bytes
`MEDIUMINT`	3 bytes
`INT`, `INTEGER`	4 bytes
`BIGINT`	8 bytes
`FLOAT(p)`	4 bytes if 0 <= `p` <= 24, 8 bytes if 25 <= `p` <= 53
`FLOAT`	4 bytes
`DOUBLE [PRECISION]`, `REAL`	8 bytes
`DECIMAL(M,D)`, `NUMERIC(M,D)`	Varies; see following discussion
`BIT(M)`	approximately (`M`+7)/8 bytes

Values for DECIMAL (and NUMERIC) columns are represented using a binary format that packs nine decimal (base 10) digits into four bytes. Storage for the integer and fractional parts of each value are determined separately. Each multiple of nine digits requires four bytes, and the “leftover” digits require some fraction of four bytes. The storage required for excess digits is given by the following table.

Leftover Digits	Number of Bytes
0	0
1	1
2	1
3	2
4	2
5	3
6	3
7	4
8	4

Storage Requirements for Date and Time Types

Data Type	Storage Required
`DATE`	3 bytes
`TIME`	3 bytes
`DATETIME`	8 bytes
`TIMESTAMP`	4 bytes
`YEAR`	1 byte

For details about internal representation of temporal values, see MySQL Internals: Important Algorithms and Structures.

Storage Requirements for String Types

In the following table, M represents the declared column length in characters for nonbinary string types and bytes for binary string types. L represents the actual length in bytes of a given string value.

Data Type	Storage Required
`CHAR(M)`	`M` × `w` bytes, 0 `<= M <=` 255, where `w` is the number of bytes required for the maximum-length character in the character set. See Section 14.6.3.12.5, “Physical Row Structure” for information about `CHAR` data type storage requirements for `InnoDB` tables.
`BINARY(M)`	`M` bytes, 0 `<= M <=` 255
`VARCHAR(M)`, `VARBINARY(M)`	`L` + 1 bytes if column values require 0 – 255 bytes, `L` + 2 bytes if values may require more than 255 bytes
`TINYBLOB`, `TINYTEXT`	`L` + 1 bytes, where `L` < 2⁸
`BLOB`, `TEXT`	`L` + 2 bytes, where `L` < 2¹⁶
`MEDIUMBLOB`, `MEDIUMTEXT`	`L` + 3 bytes, where `L` < 2²⁴
`LONGBLOB`, `LONGTEXT`	`L` + 4 bytes, where `L` < 2³²
`ENUM('value1','value2',...)`	1 or 2 bytes, depending on the number of enumeration values (65,535 values maximum)
`SET('value1','value2',...)`	1, 2, 3, 4, or 8 bytes, depending on the number of set members (64 members maximum)

Variable-length string types are stored using a length prefix plus data. The length prefix requires from one to four bytes depending on the data type, and the value of the prefix is L (the byte length of the string). For example, storage for a MEDIUMTEXT value requires L bytes to store the value plus three bytes to store the length of the value.

To calculate the number of bytes used to store a particular CHAR, VARCHAR, or TEXT column value, you must take into account the character set used for that column and whether the value contains multi-byte characters. In particular, when using the utf8 Unicode character set, you must keep in mind that not all characters use the same number of bytes and can require up to three bytes per character. For a breakdown of the storage used for different categories of utf8 characters, see Section 10.1.10, “Unicode Support”.

VARCHAR, VARBINARY, and the BLOB and TEXT types are variable-length types. For each, the storage requirements depend on these factors:

The actual length of the column value
The column's maximum possible length
The character set used for the column, because some character sets contain multi-byte characters

For example, a VARCHAR(255) column can hold a string with a maximum length of 255 characters. Assuming that the column uses the latin1 character set (one byte per character), the actual storage required is the length of the string (L), plus one byte to record the length of the string. For the string 'abcd', L is 4 and the storage requirement is five bytes. If the same column is instead declared to use the ucs2 double-byte character set, the storage requirement is 10 bytes: The length of 'abcd' is eight bytes and the column requires two bytes to store lengths because the maximum length is greater than 255 (up to 510 bytes).

The effective maximum number of bytes that can be stored in a VARCHAR or VARBINARY column is subject to the maximum row size of 65,535 bytes, which is shared among all columns. For a VARCHAR column that stores multi-byte characters, the effective maximum number of characters is less. For example, utf8 characters can require up to three bytes per character, so a VARCHAR column that uses the utf8 character set can be declared to be a maximum of 21,844 characters. See Section E.7.4, “Limits on Table Column Count and Row Size”.

The NDBCLUSTER storage engine in MySQL 5.1 supports variable-width columns. This means that a VARCHAR column in a MySQL Cluster table requires the same amount of storage as it would using any other storage engine, with the exception that such values are 4-byte aligned. Thus, the string 'abcd' stored in a VARCHAR(50) column using the latin1 character set requires 8 bytes (rather than 6 bytes for the same column value in a MyISAM table). This represents a change in behavior from earlier versions of NDBCLUSTER, where a VARCHAR(50) column would require 52 bytes storage per record regardless of the length of the string being stored.

TEXT and BLOB columns are implemented differently in the NDB Cluster storage engine, wherein each row in a TEXT column is made up of two separate parts. One of these is of fixed size (256 bytes), and is actually stored in the original table. The other consists of any data in excess of 256 bytes, which is stored in a hidden table. The rows in this second table are always 2,000 bytes long. This means that the size of a TEXT column is 256 if size <= 256 (where size represents the size of the row); otherwise, the size is 256 + size + (2000 – (size – 256) % 2000).

The size of an ENUM object is determined by the number of different enumeration values. One byte is used for enumerations with up to 255 possible values. Two bytes are used for enumerations having between 256 and 65,535 possible values. See Section 11.4.4, “The ENUM Type”.

The size of a SET object is determined by the number of different set members. If the set size is N, the object occupies (N+7)/8 bytes, rounded up to 1, 2, 3, 4, or 8 bytes. A SET can have a maximum of 64 members. See Section 11.4.5, “The SET Type”.

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[Mysql] 5.6.1 source install.. ncurses error...

ITWeb/개발일반 2013. 8. 22. 14:52

ncurses-devel 설치를 하시면 되구요.

설치 후에도 에러가 나면 cmake 시에 path 를 잡아 주시면 됩니다.

cmake \
        -DCURSES_LIBRARY=/usr/lib64/libncurses.so \
        -DCURSES_INCLUDE_PATH=/usr/include \
	-DCMAKE_INSTALL_PREFIX=/home/mysql/app/mysql \
	-DMYSQL_UNIX_ADDR=/home/mysql/app/mysql/mysql.sock \
	-DDEFAULT_CHARSET=utf8 \
	-DDEFAULT_COLLATION=utf8_general_ci \
	-DWITH_EXTRA_CHARSETS=all \
	-DMYSQL_DATADIR=/home/mysql/app/mysql/db \
	-DENABLED_LOCAL_INFILE=1 \
	-DWITH_MYISAM_STORAGE_ENGINE=1 \
	-DWITH_INNOBASE_STORAGE_ENGINE=1 \
	-DWITH_ARCHIVE_STORAGE_ENGINE=1 \
	-DWITH_BLACKHOLE_STORAGE_ENGINE=1 \
	-DWITH_MEMORY_STORAGE_ENGINE=1 \
	-DWITH_READLINE=1 \
	-DENABLED_LOCAL_INFILE=1 \
	-DMYSQL_USER=mysql \
	-DMYSQL_TCP_PORT=3306 \
	-DENABLE_DOWNLOADS=1

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jjeong

'MySQL'에 해당되는 글 16건

[MySQL] group_concat 사용 시 순서 지정.

[MySQL] HikariCP Connection Pool 관리 예.

[Docker] 로컬에 MySQL 설치 합니다.

[MySQL] mysql.user 테이블에 계정 추가하기.

[MySQL] JSON Type 사용하기

[MySQL] root password 리셋하기.

[Mysql] create database syntax example.

[MySQL] SQL JOINS 그림 설명.

11.6 Data Type Storage Requirements

11.6 Data Type Storage Requirements

Storage Requirements for `InnoDB` Tables

Storage Requirements for `NDBCLUSTER` Tables

Storage Requirements for Numeric Types

Storage Requirements for Date and Time Types

Storage Requirements for String Types

[Mysql] 5.6.1 source install.. ncurses error...

티스토리툴바

'MySQL'에 해당되는 글 16건

11.6 Data Type Storage Requirements

Storage Requirements for InnoDB Tables

Storage Requirements for NDBCLUSTER Tables

Storage Requirements for Numeric Types

Storage Requirements for Date and Time Types

Storage Requirements for String Types

티스토리툴바

Storage Requirements for `InnoDB` Tables

Storage Requirements for `NDBCLUSTER` Tables