initialization:
mysqld --initialise-secure
Database (folder) list (file) data lines (one line content file)
Database operations:
1 Database:
increase:
SQL statement:
create database database name
example:
create database db1
delete
drop database database name
drop database db1；
modify
No special modification instructions updata
Deleted rebuild
Inquire
show databases；
use
use database name;
Examples: use db1;
Data Table 2:
New:
use db1；
Version 0:
SQL statement:
create table table name (Column name Type 1);
example:
create table t1（id int，name char（32））；
increase:
instruction:
insert into table (column 1, column 2) values (value 1, value 2)
example:
insert into t1（id，name） values（1，“jack”）
insert into t2（id，name） values（2，“owen“）
Improved 1:
create table table name (Column name Type 1) engine = Innodb charset = utf8;
ps：
Engine: Innodb and MyIsam
5.5 version of the above are the default Innodb
create table t1（id int，name char（32））engine=Innodb charest = utf8；
insert into t2 (id, name) values (1, '你好');
insert into t2 (id, name) values (1, 'xxx');
Improvement 2:
Create Table table name (
column name a type AUTO_INCREMENT Primary Key
) Engine = Innodb charset = UTF8;
Create Table T4 (
ID int AUTO_INCREMENT Primary Key,
name char (32) Not null default ''
) Engine = Innodb charset = utf8;
AUTO_INCREMENT: increment
primary key: primary key index (effect: speed lookup)
not null: not null
default: default value
Note: after you back a finished, not a comma (********* )
one kind:
INSERT INTO T3 (ID, name) values (. 1, 'Hello');
INSERT INTO T3 (ID, name) values (2, 'XXX');
two kinds:
INSERT INTO T3 (name) values ( 'Hello');
INSERT INTO T3 (name) values ( 'XXX');
-------------------------------- -----------------------------
final format:
create table table (
column 1 Property [Default is null],
column 2 Property [Default is null],
.....
row n-th column attribute [Default is null]
) = Engine Storage Engine charset = character set
The final example:
Create Table T4 (
ID int Primary Key AUTO_INCREMENT,
name char (32) Not null default '',
pwd char (32) Not null default ''
) = Engine Innodb charset = UTF8;
View:
Commands:
SELECT column names from table;
example:
SELECT * from T1;
column types:
. A numeric
Create Table T4 (
ID unsigned MEDIUMINT AUTO_INCREMENT Primary Key,
name char (32) Not null default '',
pwd char (32) default null not ''
) = Engine Innodb charset = UTF8;
tinyint:
range:
signed: -128 to 127
unsigned: 0 to unsigned 255
smallint the
range:
signed: -32768 to 32767
unsigned: 0 to unsigned 65535
MEDIUMINT
range :
signed: -8388608 to 8388607
unsigned: 0 to unsigned 16777215
int
BIGINT
differences:
. a different ranges, according to their company's business choice come
b unsigned and signed meaning.
a float (M, D) float
decimal (M, D) than the fixed-point type float more precise
example: 3.1415151519868789789
float: 3.141515000000000000
decimal: 3.1415151519868789789
126.35
M: total number of decimal digit decimal (. 5,)
D: Several behind the decimal point decimal (5, 2)
be used:
for example said deposit salary pay: 6000.23 decimal (, 2)
B string type.
char: this column values of a given length char (32) is 32 advantages: speed disadvantages: waste
VARCHAR: variable length VARCHAR (32) Pro: waste, space-saving drawbacks: slow
according to their company's business come selection:
Create Table UserInfo (
ID Primary Key unsigned MEDIUMINT AUTO_INCREMENT,
name VARCHAR (128) Not null default '',
pwd char (32) Not null default '',
the create_time datetime default null not '1970-01-01 00:00:00'
) = Engine Innodb charset = UTF8;
in general, if there is no 100% certainty, are used VARCHAR ()
text: text relatively large range, if the large number of characters stored, you can use this field
c time type.
DATE 2019-6-12
recommended datetime
delete
instruction:
drop Table name;
even with all data in the data table are deleted
ps: at work, online database, this command will not let you use the
example:
drop the table T1;
inquiry
Show the tables;
desc table name;: View table structure
show create table table name: create procedure to view a table
on the primary key increment: (not focused)
Show the session Variables like 'auto_inc%';
SET the session auto_increment_increment = 2;
Show Global Variables like 'auto_inc%';
SET Global auto_increment_increment = 2;
modified
Create Table T4 (
ID int AUTO_INCREMENT Primary key,
name char (32) Not null default '',
pwd char (32) Not null default ''
) engine = Innodb charset = utf8;
editable field:
ALTER Table table name (t3) change the original column name (name) a new column name (username varchar (32) not null default '');
new field:
ALTER Table table name ( t3) add new columns (pwd char (32) not null default '');
delete field:
ALTER table table name (t3) drop column name (pwd);
3. Data lines:
increasing
insert into t3 (id, name) values (1, ' Hello');
query
select * from t3;: all of the columns in the table are listed all the
select column names, column names, column names from t3: the value of a column. isolated
delete
delete from table name (t3); deletes all the data in the table out, once again, when added, will continue on a continuing ID
TRUNCATE table name (t3); the table All data deleted, added again when, ID will re-start
truncate speed
ps: work, online database, this command will not let you use the
delete from table name (t3) where name = 'xxxxx ' ;
modify
Update SET username = T3 'Zekai';
Update SET username = T3 'XXXX' WHERE ID =. 3;
Update SET username = T3 'XXXX', pwd = 'XXXXX' WHERE ID =. 3;
Seven foreign key: (**************************** ************************************************************)
disadvantages:
1. data repeat
2. If the department is too long, too much space
solution:
re-design a table, this table stores sector information
department table:
Create table department (
ID int AUTO_INCREMENT Primary Key,
depart_name VARCHAR (32) Not null default ''
) Engine = Innodb charset = UTF8;
INSERT INTO department (depart_name) values ( 'PR') , ( 'oFF oFF'), ( 'Guan');
Create Table UserInfo (
ID int AUTO_INCREMENT Primary key,
name VARCHAR (32) Not null default '',
depart_id int Not null default. 1,
# constraint foreign key name (fk_userinfo_depart) foreign key (column name (depart_id)) references the table name (Department) (column name associated (id)),
constraint fk_userinfo_depart Foreign Key (depart_id) References Department (ID)
) Engine = Innodb charset = UTF8;
INSERT INTO UserInfo (name, depart_id) values ( 'the root1',. 1);
INSERT INTO UserInfo (name, depart_id) values ( 'root2' , 2); wrong
Note:
Creating multiple foreign key, the name can not be the same