Introduction to database
1concept
()
2History of database development
refers to the storage and management of data based on the network model that records the type of nodes.
To organize and manage data databases.
The relational model is“
),DB2(IBM)
Microsoft Corp),MySQL()
Microsoft Corp)
noSQL
MangoDB,Redis
5sqlbrief introduction
Structure Query Language
can be passed.Window
2Login to MySQL database server
” document, the operating environment iscmd
mysql -h > port number-u-p password
explains:
-h mysql” means the machine. 127.0.0.1” means the machine. If it is the machine, it can be omitted.
-P default, it can be omitted.
-u >root password ” is not recommended.-p()
3mysqlHierarchical structure
DBMS DataBase Management System
Table corresponds to the form in reality.)
Record
Three basic operation of database
1view the database
Grammar:
show databases;
explains:
testMySQL2 creating database in song style
explains:
(“) > is used to set the stored character set.
collate
>:
> ended. The role of semicolons and cars is to connect customers.cmd
show create database explains:
4Delete database
;
5Select database
;
explains:
database, it is necessary to enter the specified database first.
> can view database information, which contains the database information currently in existence.
Four basic operation of data tables
1Set up the client’s communication code.
> client
explains:
What is the code for the current client to communicate with the server?
2View data tables
explains:
3Create data tables
(
> Field > Table option.
explains:
The data type in the corresponding program
【Table options]
charset >
engine storage engine
( heading)
4View table structure
;
5View the creation statement of the table
;
6Delete table
;
Five basic operation of data
1Add data
()values()
explains:
value list of the song body must be quoted.
> fields can also be omitted, if omission indicates that all fields are inserted into the data. The order of the value list is consistent with the order of the fields in the table.
2View the data
①、 > Fields from where clause”.group by clause”.having clause”.order by clause”.limit explains:
* All fields
is used to view some fields.
Examples:
②、where
wherewhere” clause in the song style is used to screen the records. That is, the expression will involve the operator.
MySQL,<,>=,<=,<>,=,and,or,not,between m and n,in(),is null,like
= ” is used to judge whether it is unequal or assignment operator.
and,or Logic and logic or
between m and n n > value list) is only for judgement.null > placeholder:%,_
% represents the current position and its post.0 or more characters.
_
:between m and n
3Modifying the data
set , ,… where ：
where indicates that all records match.
4Delete data
where explains:
where
> view data:select >
1Numeric type
①、Integer type
The integer type is a series, all integers, the only difference is that the number can be represented by the same size.
②、 decimal type
):
double
Grammar:
float(m,d)
double(m,d)
explains:
m represents the total number.
d represents the decimal place.
m-d
explains:
“float5 to the song body.60 replace
“double14 to the song body.15 replace
decimal( fixed-point type):
explains:
m ” represents the total number.,m65
d represents the decimal place.,d
2Character
①、Fixed length
represents the number of characters. The biggest is255“.
②、Change length
represents the number of characters.The theory is 65535.” will be subject to many conditions.)
Examples:
③、Text type
text is also a series, including
tinytext,text,mediumtext,longtext④、blob type
blob > is also a series, including
tinyblob,blob,mediumblob,longblob“?
blog⑤、Enumerated type
” is used to standardize data, and only allows users to select one from a number of predetermined data.
Grammar:
enum()
⑥、Set type
” is used to standardize data, allowing users to select more than one predetermined number of data.
Grammar:
set()
Examples:
3 date time type
year(2 or4) 2;44
date format: ‘2017-12-4’
time format: ’17:14:59′
datetime date time type
Seven character set and proofreading set
1character set
①、SeeMySQL
2Validation set
A checkset is a comparison rule in a set of characters. That is, case sensitive.
show collation;
Tips:
()
_ci CaseInsensitive > no case sensitive.)
_bin > case sensitive
verification set is mainly reflected in comparison.
