Ubuntu18.04安装MySQL及Demos

1.查看有没有安装MySQL

dpkg -l | grep mysql
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我的电脑已经安装过了

Three@Randy:~$ dpkg -l | grep mysql
ii  default-libmysqlclient-dev:amd64                                 1.0.4                                           amd64        MySQL database development files (metapackage)
ii  libmysqlclient-dev                                               5.7.39-0ubuntu0.18.04.2                         amd64        MySQL database development files
ii  libmysqlclient20:amd64                                           5.7.39-0ubuntu0.18.04.2                         amd64        MySQL database client library
ii  libpocodatamysql50                                               1.8.0.1-1ubuntu4                                amd64        C++ Portable Components (POCO) Data MySQL library
ii  libqt4-sql-mysql:amd64                                           4:4.8.7+dfsg-7ubuntu1                           amd64        Qt 4 MySQL database driver
ii  mysql-client                                                     5.7.39-0ubuntu0.18.04.2                         all          MySQL database client (metapackage depending on the latest version)
ii  mysql-client-5.7                                                 5.7.39-0ubuntu0.18.04.2                         amd64        MySQL database client binaries
ii  mysql-client-core-5.7                                            5.7.39-0ubuntu0.18.04.2                         amd64        MySQL database core client binaries
ii  mysql-common                                                     5.8+1.0.4                                       all          MySQL database common files, e.g. /etc/mysql/my.cnf
ii  mysql-server                                                     5.7.39-0ubuntu0.18.04.2                         all          MySQL database server (metapackage depending on the latest version)
iF  mysql-server-5.7                                                 5.7.39-0ubuntu0.18.04.2                         amd64        MySQL database server binaries and system database setup
ii  mysql-server-core-5.7                                            5.7.39-0ubuntu0.18.04.2                         amd64        MySQL database server binaries
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2.安装mysql

apt install mysql-server

# python  
# 前置条件
sudo apt-get install python-dev libmysqlclient-dev # Ubuntu
sudo yum install python-devel mysql-devel # Red Hat / CentOS
# 安装
pip install MySQL-python
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安装后检查是否安装成功

netstat -tap | grep mysql
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Three@Randy:~$ netstat -tap | grep mysql
(Not all processes could be identified, non-owned process info
 will not be shown, you would have to be root to see it all.)
tcp        0      0 randy:34644      10.88.88.88:mysql        ESTABLISHED 31547/mysql 
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3.检查mysql服务状态

systemctl status mysql
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Three@Randy:~$ systemctl status mysql
● mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Mon 2022-08-08 08:51:57 CST; 59min ago

8月 08 08:51:55 randy systemd[1]: Starting MySQL Community Server...
8月 08 08:51:55 randy mysqld[8752]: Initialization of mysqld failed: 0
8月 08 08:51:55 randy systemd[1]: mysql.service: Control process exited, code=exited status=1
8月 08 08:51:57 randy systemd[1]: mysql.service: Failed with result 'exit-code'.
8月 08 08:51:57 randy systemd[1]: Stopped MySQL Community Server.
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4.mysql命令

Three@Randy:~$ mysql - help
mysql  Ver 14.14 Distrib 5.7.39, for Linux (x86_64) using  EditLine wrapper
Copyright (c) 2000, 2022, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Usage: mysql [OPTIONS] [database]
  -?, --help          Display this help and exit.
  -I, --help          Synonym for -?
  --auto-rehash       Enable automatic rehashing. One doesn't need to use
                      'rehash' to get table and field completion, but startup
                      and reconnecting may take a longer time. Disable with
                      --disable-auto-rehash.
                      (Defaults to on; use --skip-auto-rehash to disable.)
  -A, --no-auto-rehash 
                      No automatic rehashing. One has to use 'rehash' to get
                      table and field completion. This gives a quicker start of
                      mysql and disables rehashing on reconnect.
  --auto-vertical-output 
                      Automatically switch to vertical output mode if the
                      result is wider than the terminal width.
  -B, --batch         Don't use history file. Disable interactive behavior.
                      (Enables --silent.)
  --bind-address=name IP address to bind to.
  --binary-as-hex     Print binary data as hex
  --character-sets-dir=name 
                      Directory for character set files.
  --column-type-info  Display column type information.
  -c, --comments      Preserve comments. Send comments to the server. The
                      default is --skip-comments (discard comments), enable
                      with --comments.
  -C, --compress      Use compression in server/client protocol.
  -#, --debug[=#]     This is a non-debug version. Catch this and exit.
  --debug-check       This is a non-debug version. Catch this and exit.
  -T, --debug-info    This is a non-debug version. Catch this and exit.
  -D, --database=name Database to use.
  --default-character-set=name 
                      Set the default character set.
  --delimiter=name    Delimiter to be used.
  --enable-cleartext-plugin 
                      Enable/disable the clear text authentication plugin.
  -e, --execute=name  Execute command and quit. (Disables --force and history
                      file.)
  -E, --vertical      Print the output of a query (rows) vertically.
  -f, --force         Continue even if we get an SQL error.
  --histignore=name   A colon-separated list of patterns to keep statements
                      from getting logged into syslog and mysql history.
  -G, --named-commands 
                      Enable named commands. Named commands mean this program's
                      internal commands; see mysql> help . When enabled, the
                      named commands can be used from any line of the query,
                      otherwise only from the first line, before an enter.
                      Disable with --disable-named-commands. This option is
                      disabled by default.
  -i, --ignore-spaces Ignore space after function names.
  --init-command=name SQL Command to execute when connecting to MySQL server.
                      Will automatically be re-executed when reconnecting.
  --local-infile      Enable/disable LOAD DATA LOCAL INFILE.
  -b, --no-beep       Turn off beep on error.
  -h, --host=name     Connect to host.
  -H, --html          Produce HTML output.
  -X, --xml           Produce XML output.
  --line-numbers      Write line numbers for errors.
                      (Defaults to on; use --skip-line-numbers to disable.)
  -L, --skip-line-numbers 
                      Don't write line number for errors.
  -n, --unbuffered    Flush buffer after each query.
  --column-names      Write column names in results.
                      (Defaults to on; use --skip-column-names to disable.)
  -N, --skip-column-names 
                      Don't write column names in results.
  --sigint-ignore     Ignore SIGINT (CTRL-C).
  -o, --one-database  Ignore statements except those that occur while the
                      default database is the one named at the command line.
  --pager[=name]      Pager to use to display results. If you don't supply an
                      option, the default pager is taken from your ENV variable
                      PAGER. Valid pagers are less, more, cat [> filename],
                      etc. See interactive help (\h) also. This option does not
                      work in batch mode. Disable with --disable-pager. This
                      option is disabled by default.
  -p, --password[=name] 
                      Password to use when connecting to server. If password is
                      not given it's asked from the tty.
  -P, --port=#        Port number to use for connection or 0 for default to, in
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
                      /etc/services, built-in default (3306).
  --prompt=name       Set the mysql prompt to this value.
  --protocol=name     The protocol to use for connection (tcp, socket, pipe,
                      memory).
  -q, --quick         Don't cache result, print it row by row. This may slow
                      down the server if the output is suspended. Doesn't use
                      history file.
  -r, --raw           Write fields without conversion. Used with --batch.
  --reconnect         Reconnect if the connection is lost. Disable with
                      --disable-reconnect. This option is enabled by default.
                      (Defaults to on; use --skip-reconnect to disable.)
  -s, --silent        Be more silent. Print results with a tab as separator,
                      each row on new line.
  -S, --socket=name   The socket file to use for connection.
  --ssl-mode=name     SSL connection mode.
  --ssl               Deprecated. Use --ssl-mode instead.
                      (Defaults to on; use --skip-ssl to disable.)
  --ssl-verify-server-cert 
                      Deprecated. Use --ssl-mode=VERIFY_IDENTITY instead.
  --ssl-ca=name       CA file in PEM format.
  --ssl-capath=name   CA directory.
  --ssl-cert=name     X509 cert in PEM format.
  --ssl-cipher=name   SSL cipher to use.
  --ssl-key=name      X509 key in PEM format.
  --ssl-crl=name      Certificate revocation list.
  --ssl-crlpath=name  Certificate revocation list path.
  --tls-version=name  TLS version to use, permitted values are: TLSv1, TLSv1.1,
                      TLSv1.2
  --server-public-key-path=name 
                      File path to the server public RSA key in PEM format.
  --get-server-public-key 
                      Get server public key
  -t, --table         Output in table format.
  --tee=name          Append everything into outfile. See interactive help (\h)
                      also. Does not work in batch mode. Disable with
                      --disable-tee. This option is disabled by default.
  -u, --user=name     User for login if not current user.
  -U, --safe-updates  Only allow UPDATE and DELETE that uses keys.
  -U, --i-am-a-dummy  Synonym for option --safe-updates, -U.
  -v, --verbose       Write more. (-v -v -v gives the table output format).
  -V, --version       Output version information and exit.
  -w, --wait          Wait and retry if connection is down.
  --connect-timeout=# Number of seconds before connection timeout.
  --max-allowed-packet=# 
                      The maximum packet length to send to or receive from
                      server.
  --net-buffer-length=# 
                      The buffer size for TCP/IP and socket communication.
  --select-limit=#    Automatic limit for SELECT when using --safe-updates.
  --max-join-size=#   Automatic limit for rows in a join when using
                      --safe-updates.
  --secure-auth       Refuse client connecting to server if it uses old
                      (pre-4.1.1) protocol. Deprecated. Always TRUE
  --server-arg=name   Send embedded server this as a parameter.
  --show-warnings     Show warnings after every statement.
  -j, --syslog        Log filtered interactive commands to syslog. Filtering of
                      commands depends on the patterns supplied via histignore
                      option besides the default patterns.
  --plugin-dir=name   Directory for client-side plugins.
  --default-auth=name Default authentication client-side plugin to use.
  --binary-mode       By default, ASCII '\0' is disallowed and '\r\n' is
                      translated to '\n'. This switch turns off both features,
                      and also turns off parsing of all clientcommands except
                      \C and DELIMITER, in non-interactive mode (for input
                      piped to mysql or loaded using the 'source' command).
                      This is necessary when processing output from mysqlbinlog
                      that may contain blobs.
  --connect-expired-password 
                      Notify the server that this client is prepared to handle
                      expired password sandbox mode.

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf 
The following groups are read: mysql client
The following options may be given as the first argument:
--print-defaults        Print the program argument list and exit.
--no-defaults           Don't read default options from any option file,
                        except for login file.
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
                        Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
auto-rehash                       TRUE
auto-vertical-output              FALSE
bind-address                      (No default value)
binary-as-hex                     FALSE
character-sets-dir                (No default value)
column-type-info                  FALSE
comments                          FALSE
compress                          FALSE
database                          (No default value)
default-character-set             auto
delimiter                         ;
enable-cleartext-plugin           FALSE
vertical                          FALSE
force                             FALSE
histignore                        (No default value)
named-commands                    FALSE
ignore-spaces                     FALSE
init-command                      (No default value)
local-infile                      FALSE
no-beep                           FALSE
host                              (No default value)
html                              FALSE
xml                               FALSE
line-numbers                      TRUE
unbuffered                        FALSE
column-names                      TRUE
sigint-ignore                     FALSE
port                              0
prompt                            mysql> 
quick                             FALSE
raw                               FALSE
reconnect                         TRUE
socket                            (No default value)
ssl                               TRUE
ssl-verify-server-cert            FALSE
ssl-ca                            (No default value)
ssl-capath                        (No default value)
ssl-cert                          (No default value)
ssl-cipher                        (No default value)
ssl-key                           (No default value)
ssl-crl                           (No default value)
ssl-crlpath                       (No default value)
tls-version                       (No default value)
server-public-key-path            (No default value)
get-server-public-key             FALSE
table                             FALSE
user                              (No default value)
safe-updates                      FALSE
i-am-a-dummy                      FALSE
connect-timeout                   0
max-allowed-packet                16777216
net-buffer-length                 16384
select-limit                      1000
max-join-size                     1000000
secure-auth                       TRUE
show-warnings                     FALSE
plugin-dir                        (No default value)
default-auth                      (No default value)
binary-mode                       FALSE
connect-expired-password          FALSE
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5.连接数据库

# 连接主机为10.88.88.88的数据库
mysql -h 10.88.88.88 -u Three -p
# 直接连接到mysql 名为randy_db的数据库
mysql -h 10.88.88.88 -u Three -p  -D randy_db
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Three@Randy:~$ mysql -h 10.88.88.88 -u Three -p
Enter password: 
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 569
Server version: 5.7.33-0ubuntu0.16.04.1 (Ubuntu)

Copyright (c) 2000, 2022, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
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5.1查看数据库

show databases;
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mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| randy_db              |
+--------------------+
2 rows in set (0.01 sec)
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5.2进入数据库randy_db

mysql> use randy_db
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
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5.3查看数据库中有哪些表

show tables
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mysql> show tables;
+-----------------+
| Tables_in_randy_db |
+-----------------+
| box_table       |
| frame_table     |
+-----------------+
2 rows in set (0.00 sec)
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5.4 demos

SELECT

SELECT
{* | <字段列名>}
[
FROM <表 1>, <表 2>…
[WHERE <表达式>
[GROUP BY 
[HAVING  [{ }…]]
[ORDER BY ]
[LIMIT[,] ]
]
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各条件句的含义如下：

• {*|<字段列名>}包含星号通配符的字段列表，表示所要查询字段的名称。
• <表 1>，<表 2>…，表 1 和表 2 表示查询数据的来源，可以是单个或多个。
• WHERE <表达式>是可选项，如果选择该项，将限定查询数据必须满足该查询条件。
• GROUP BY< 字段 >，该子句告诉 MySQL 如何显示查询出来的数据，并按照指定的字段分组。
• [ORDER BY< 字段 >]，该子句告诉 MySQL 按什么样的顺序显示查询出来的数据，可以进行的排序有升序（ASC）和降序（DESC），默认情况下是升序。
• [LIMIT[，]]，该子句告诉 MySQL 每次显示查询出来的数据条数。

COUNT() 函数统计数据表中包含的记录行的总数，或者根据查询结果返回列中包含的数据行数

• COUNT(*) 计算表中总的行数，无论某列有数值或者为空值。
• COUNT(表达式) 计算不包含NULL值的行数。
• COUNT(DISTINCT 表达式) 返回不包含NULL值的唯一行数

COUNT()函数的返回类型为BIGINT。 如果没有找到匹配的行，则COUNT()函数返回0。

查询行数

mysql> select count(*) from frame_table;
+----------+
| count(*) |
+----------+
|       60 |
+----------+
1 row in set (0.00 sec)
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分类统计个数,按唯一行统计

mysql>  select count(distinct id) from frame_table;
+--------------------+
| count(distinct id) |
+--------------------+
|                 60 |
+--------------------+
1 row in set (0.01 sec)
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分类统计个数

mysql> select self_state,count(*) from frame_table group by self_state;
+------------------------+----------+
| self_state             | count(*) |
+------------------------+----------+
| front                  |       51 |
| left                   |        2 |
| right                  |        7 |
+------------------------+----------+
3 rows in set (0.00 sec)
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分类基础上，筛选出个数超过5的类别，使用HAVING

mysql> select self_state,count(*) from frame_table group by self_state having count(*) >= 5;
+-------------+----------+
| self_state  | count(*) |
+-------------+----------+
| front       |       51 |
| right       |        7 |
+-------------+----------+
2 rows in set (0.00 sec)
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按条件查询 Where

mysql> select * from frame_table where first_scene = 'Construction_road,Accident_road' and second_scene = 'crossroads';
< Randy: hide the data>
9 rows in set (0.00 sec)

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MySQL COUNT IF

可以使用COUNT函数中的控制流程功能，例如IF，IFNULL，CASE等来计数其值与条件匹配的行。

select count(IF(abs(distance) <= 50.0,1,NULL)) '0-50.0',
                  count(IF(50.0 < abs(distance) and abs(distance) <= 100.0,1,NULL)) '50.0-100.0',
                  count(IF(100.0 < abs(distance) and abs(distance) <= 150.0,1,NULL)) '100.0-150.0',
                  count(IF(150.0 < abs(distance) and abs(distance) <= 200.0,1,NULL)) '150.0-200.0'
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执行得到以下结果

+--------+------------+-------------+-------------+
| 0-50.0 | 50.0-100.0 | 100.0-150.0 | 150.0-200.0 |
+--------+------------+-------------+-------------+
|    835 |        513 |          92 |           4 |
+--------+------------+-------------+-------------+
1 row in set (0.01 sec)
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如果abs(distance)在范围内，if函数将返回1,否则返回NULL。Count函数只计数1,而不是NULL值。