比CRUD多一點兒（一）：MySQL經常使用命令

比CRUD多一點兒（一）：MySQL經常使用命令

這是MySQL系列筆記的第一部分，本系列筆記但願能按照筆者本身學習MySQL技術的經從來記錄，避免純粹按照內容一塊一塊總結，也就是不一樣於通常按內容分配章節的書籍的結構，有一個平滑的閱讀曲線。內容比較豐富的技術點會按照專題在多個學習筆記中逐漸深刻。文章列表點此。

首先，請若是還徹底爲接觸過MySQL的讀者先閱讀w3c的SQL教程，再來讀本篇內容。

這部分的標題叫比CRUD多一丁點兒，比起最基礎的w3c的SQL教程以外，只多一點的擴展，知足應付從純粹閱讀入門資料到能夠上手完成一個簡單的工做的需求。

第一篇的主要內容會是最經常使用的一些mysql命令。由於雖然有不少圖形化的工具，但在實際的工做中由於須要去線上服務查看數據，處理問題，字符界面的命令行工具是必不可少的。

客戶端程序mysql:

鏈接交互式終端

mysql -h $host -P $port -u $user -p$passsword $database_name

例如用戶root使用密碼mydb@xxx用連接到地址爲192.168.1.99，端口爲3306的數mysql進程，並默認使用上名爲testdb的數據庫（即自動執行use testdb）。

mysql -h 192.168.1.99 -P 3306 -u"root" -p"mydb@xx" testdb

各參數若是有@,&等bash的關鍵字，則須要用""引發來。

非交互式的執行SQL

有時候須要在命令行執行某句SQL，則建議使用 -Bse 參數。-B參數的含義是執行多條語句(batch)這樣能夠執行多條，-e便是執行(execute)，-s參數意思是靜默執行(silent)可讓輸出格式精簡一些。

mysql -h $host -P $port -u $user -p$passsword -Bse "command1;command2;....;commandn"

例如，常見的將執行結果導出到文件中方便留存和閱讀。

mysql -h 192.168.1.99 -P 3306 -u"root" -p"mydb@xx" -Bse "select id,name from testdb.Account;" > result.txt

導出程序mysqldump

mysqldump是作數據導出的命令行工具，也是mysql安裝後默認會帶的。做用是將mysql數據庫中的數據導出出來。

導出特定的表的內容

mysql -h $host -P $port -u $user -p$passsword $database_name $table1 $table2 ...

例如

mysqldump -h 192.168.1.99 -P 3306 -u"root" -p"mydb@xx" mydb table1 table2 > result.sql

只導出表結構

使用--no-data參數只導出表結構，

mysqldump -h 192.168.1.99 -P 3306 -u"root" -p"mydb@xx" --no-data mydb  > result.sql

比較表結構mysqldiff

在開發實踐中不免會遇到校驗數據表結構不一樣，或者根據開發環境和目標環境的表結構不一樣來生成對應的表結構修改語句。mysql在5.7版本就提供了一個自帶的mysqldiff工具。參數比較多，直接舉例說明生成difftype=sql的ALTER語句的命令寫法，以下：

mysqldiff --server1=root@host1 --server2=root@host2 \
          --show-reverse --difftype=sql \
          db1.table1:dbx.table3

# server1 on host1: ... connected.
# server2 on host2: ... connected.
# Comparing db1.table1 to dbx.table3                               [FAIL]
# Transformation statements:

# --destination=server1:
ALTER TABLE db1.table1
  ADD COLUMN notes char(30) AFTER a,
  CHANGE COLUMN misc misc char(55);

# --destination=server2:
# ALTER TABLE dbx.table3
#   DROP COLUMN notes,
#   CHANGE COLUMN misc misc char(30);

具體看mysql的官方文檔：https://dev.mysql.com/doc/mys...

若是在mysql5.7版本如下就使用mysqldump命令參數輸出簡潔的表結構，隨後diff文件而後自行編寫ALTER語句吧。

mysqldump --skip-comments --skip-extended-insert -u root -p dbName1>file1.sql
mysqldump --skip-comments --skip-extended-insert -u root -p dbName2>file2.sql
diff file1.sql file2.sql

內建?, \s命令

心急火燎的進入mysql終端處理線上問題，這時候一個語法拼不對，還得切出去查手冊？萬一環境是內網不能上網就更是麻煩，其實mysql內建了幫助手冊，能夠直接在終端查詢。

? 是交互式mysql終端內建的幫助命令。能夠按照此幫助查閱文檔等。其輸出以下

mysql> ?

For information about MySQL products and services, visit:
   http://www.mysql.com/
For developer information, including the MySQL Reference Manual, visit:
   http://dev.mysql.com/
To buy MySQL Enterprise support, training, or other products, visit:
   https://shop.mysql.com/

List of all MySQL commands:
Note that all text commands must be first on line and end with ';'
?         (\?) Synonym for `help'.
clear     (\c) Clear the current input statement.
connect   (\r) Reconnect to the server. Optional arguments are db and host.
delimiter (\d) Set statement delimiter.
edit      (\e) Edit command with $EDITOR.
ego       (\G) Send command to mysql server, display result vertically.
exit      (\q) Exit mysql. Same as quit.
go        (\g) Send command to mysql server.
help      (\h) Display this help.
nopager   (\n) Disable pager, print to stdout.
notee     (\t) Don't write into outfile.
pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
print     (\p) Print current command.
prompt    (\R) Change your mysql prompt.
quit      (\q) Quit mysql.
rehash    (\#) Rebuild completion hash.
source    (\.) Execute an SQL script file. Takes a file name as an argument.
status    (\s) Get status information from the server.
system    (\!) Execute a system shell command.
tee       (\T) Set outfile [to_outfile]. Append everything into given outfile.
use       (\u) Use another database. Takes database name as argument.
charset   (\C) Switch to another charset. Might be needed for processing binlog with multi-byte charsets.
warnings  (\W) Show warnings after every statement.
nowarning (\w) Don't show warnings after every statement.
resetconnection(\x) Clean session context.

\s 可查看當前狀態，版本，客戶端ip，QPS等，\!能夠在mysql終端中執行shell命令。在是不少處理問題的時候終端界面一進入mysql的交互式終端，就找不到ip、端口等在bash中的信息了又須要頻繁切出，這兩個命令都很是有用。\s輸出以下：

mysql> \s
--------------
mysql  Ver 14.14 Distrib 5.7.12, for osx10.11 (x86_64) using  EditLine wrapper



Connection id:        2
Current database:    rizhiyi_system
Current user:        root@localhost
SSL:            Not in use
Current pager:        less
Using outfile:        ''
Using delimiter:    ;
Server version:        5.7.12 MySQL Community Server (GPL)
Protocol version:    10
Connection:        127.0.0.1 via TCP/IP
Server characterset:    utf8
Db     characterset:    utf8
Client characterset:    utf8
Conn.  characterset:    utf8
TCP port:        3306
Uptime:            21 sec

Threads: 1  Questions: 74  Slow queries: 0  Opens: 171  Flush tables: 1  Open tables: 164  Queries per second avg: 3.523
--------------

? contents 能夠看內建的幫助手冊

mysql> ? contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration
   Compound Statements
   Data Definition
   Data Manipulation
   Data Types
   Functions
   Functions and Modifiers for Use with GROUP BY
   Geographic Features
   Help Metadata
   Language Structure
   Plugins
   Procedures
   Storage Engines
   Table Maintenance
   Transactions
   User-Defined Functions
   Utility

而後就能夠繼續查看子菜單幫助手冊的內容，好比? Functions

mysql> ? Functions
You asked for help about help category: "Functions"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Bit Functions
   Comparison operators
   Control flow functions
   Date and Time Functions
   Encryption Functions
   Information Functions
   Logical operators
   Miscellaneous Functions
   Numeric Functions
   String Functions

? insert 幫助命令還能夠直接按關鍵字進行模糊查詢，如：

mysql> ? insert
Name: 'INSERT'
Description:
Syntax:
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name,...)]
    [(col_name,...)]
    {VALUES | VALUE} ({expr | DEFAULT},...),(...),...
    [ ON DUPLICATE KEY UPDATE
      col_name=expr
        [, col_name=expr] ... ]

Or:

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name,...)]
    SET col_name={expr | DEFAULT}, ...
    [ ON DUPLICATE KEY UPDATE
      col_name=expr
        [, col_name=expr] ... ]

Or:

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name,...)]
    [(col_name,...)]
    SELECT ...
    [ ON DUPLICATE KEY UPDATE
      col_name=expr
        [, col_name=expr] ... ]

INSERT inserts new rows into an existing table. The INSERT ... VALUES
and INSERT ... SET forms of the statement insert rows based on
explicitly specified values. The INSERT ... SELECT form inserts rows
selected from another table or tables. INSERT ... SELECT is discussed
further in [HELP INSERT SELECT].

When inserting into a partitioned table, you can control which
partitions and subpartitions accept new rows. The PARTITION option
takes a comma-separated list of the names of one or more partitions or
subpartitions (or both) of the table. If any of the rows to be inserted
by a given INSERT statement do not match one of the partitions listed,
the INSERT statement fails with the error Found a row not matching the
given partition set. See
http://dev.mysql.com/doc/refman/5.7/en/partitioning-selection.html, for
more information and examples.

In MySQL 5.7, the DELAYED keyword is accepted but ignored by the
server. See [HELP INSERT DELAYED], for the reasons for this.

URL: http://dev.mysql.com/doc/refman/5.7/en/insert.html

本文中經常使用命令的更詳細內容可看MySQL手冊：
https://dev.mysql.com/doc/refman/5.7/en/programs-overview.html