MySQL Common Command Collation summary

#修改字段类型
ALTER TABLE ' TABLE_NAME ' modify column IP varchar (50);

#增加字段
ALTER TABLE ' table_name ' Add IP varchar (50);

#增加PRIMARY key (primary key index)
ALTER TABLE ' table_name ' ADD PRIMARY KEY (' IP ');

#添加UNIQUE (unique index)
ALTER TABLE ' table_name ' ADD UNIQUE (' IP ');

#添加INDEX (normal index)
ALTER TABLE ' table_name ' ADD INDEX IP (' ip ');

#添加联合索引
ALTER TABLE ' table_name ' ADD INDEX userip (' IP ', ' name ');

#添加FULLTEXT (full-text index)
ALTER TABLE ' table_name ' ADD fulltext (' column ');

#删除索引
ALTER TABLE ' TABLE_NAME ' drop index IP;

GRANT all privileges on * * to ' root ' @ ' 192.168.3.150 ' identified by
' MyPassword ' with GRANT OPTION;

#新增一个用户名test, password 123 user link host is localhost, can also be written as IP, or 192.168.0.% ( 192.168.0. Any), or% (do not restrict host)
Insert into Mysql.user (host,user,password,ssl_cipher,x509_issuer,x509_subject) VALUES ("localhost", "Test", Password ("123"), ', ', ', ');
#新增完成后刷新权限表
Flush privileges;

#授权相关

#授权所有数据库的权限给用户名为test密码为123的用户
Grant all privileges on * * to [e-mail protected] identified by ' 123 ';

#授权所有数据库的权限给用户名为test密码为123的用户, and test has permissions granted to other users
Grant all privileges on * * to [email protected] identified by ' 123 ' with GRANT OPTION;

#授权testdb数据库的select权限给用户名为test密码为123的用户
Grant Select on testdb.* to [e-mail protected] identified by ' 123 ';

#授权完成后刷新权限表
Flush privileges;

#字段类型

The column types of the numeric type include integer and floating-point categories.

Tinyint:1 byte very small positive integer with symbol: -128~127, unsigned: 0~255
Smallint:2 byte Small Integer, signed: -32768~32767, unsigned: 0~65535
Mediumint:3 byte medium-sized integer, signed: -8388608~8388607, unsigned: 0~16777215
Int:4 byte Standard Integer, signed: -2147483648~2147483647, unsigned: 0~4294967295
Bigint:8 byte Large Integer, signed: -9223372036854775808~9233372036854775807, unsigned: 0~18446744073709551615
Float:4 byte single-precision floating-point number, minimum non-0 value: +-1.175494351e-38, maximum non-0 value: +-3.402823466e+38
Double:8 byte double-precision floating-point number, minimum non-0 value: +-2.2250738585072014e-308, maximum non-0 value: +-1.7976931348623157e+308
DECIMAL (M, D): The m+2 byte is a floating-point number expressed as a string, and its range of values is variable, determined by the values of M and D.

Character type
One character, one byte, one kanji = 2 characters, 2 bytes

Char[(m)] M-byte fixed length
Varchar[(m)] M byte variable length, storage size is the actual length of bytes of input data
Tinyblod,tinytext 2^8-1 bytes l+1 bytes
Blob,text 2^16-1 byte l+2
Mediumblob,mediumtext 2^24-1 byte l+3
Longblob,longtext 2^32-1 byte l+4
ENUM (' value1 ', ' value2 ',...) 65,535 members 1 or 2 bytes
SET (' value1 ', ' value2 ',...) 64 members 1,2,3,4 or 8 bytes

MySQL Common Command Collation summary