<>mysql Basic syntax of database

<>DDL operation

* Create database
grammar :create database Database name ;
* View all databases
grammar :show databases;
* switch ( use ) database
grammar :use + Database name ;
* Create a table
grammar :create table Table name (
Field name 1 Field type ,
Field name 2 Field type ,
Field name 3 Field type ,
…… ……
);
* View all tables in the database
grammar : Show tables;
* View the structure of the table
grammar :desc Table name ;
* Add field
grammar :alter table Table name add Field name Field type
* Delete field
grammar :alter table Table name drop Field name
* Modify table name
grammar :rename table Old table name to New table name
* Modify field type
grammar :alter table Table name modify Field name Field of new type
* Field rename
grammar :alter table Table name change Old field name New field name Field type
<>DML operation

* insert data
grammar :insert into Table name ( Field name ) value( content )
* Delete data
grammar :Delete from Table name where condition
* Modify data
grammar :update Table name set field = Revised content where ( Restrictions )
* View data
grammar :select Field name from Table name where condition
* Delete table
grammar :drop table Table name ;
truncate table Table name ;
* Delete database
drop database Library name ;
notes :
(1)Delete Only deleting the records inserted in the table does not delete them
(2)Truncate Delete data and records , Equivalent to first drop Where is this form create This is a list
<> constraint

* Characteristics of primary key constraints : Uniqueness , Non emptiness
Set primary key and auto grow
Primary key : When creating a table , After the field you want to set as the primary key Add primary key (primary key)
Self growth : When creating a table , After the field to be set to self growing Add on auto_increment
* Nonempty constraint : Cannot be empty
Add the not null
* Foreign key constraints :
To create a table based on the primary key of the main table
After field definition Add foreign key
Constraint ( Foreign key name ) foreign key( Constrained fields ) references Primary table name ( The outside world constrains its fields )
The main table as a constrained field needs to be the primary key of the table
<>DQL operation

* Basic query
Query all :
select * from Table name
Query the data of the specified column :
Select Listing 1, Listing 2…… from Table name Where to write ( What time ) Which column do you want to check
* View tables in other databases in the current database
Show tables in Database name
* View the data of the table below the non current database
Select Listing from bank.user;
* Where query criteria
Relational operators :> < = != >= <=
section :between A and B(A and B between )【A,B】
AND && and also
or || : or
not: wrong Negation
Is null: It's empty
is not null : Not empty
in In what contain
* Fuzzy query
Like image
wildcard
_: Any character
%: Any number of

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