Most commonly used SQL statements

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grammar ：

Step by step from shallow to deep , It's all used here mysql It's done .

Basics ：

Connect to database ：

mysql -h10.20.66.32 -uroot -p123456

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-h And then mysqlServer Address ,-u Followed by the user name ,-p And then there's the code .

view the database

show databases;

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Using a database

use test;

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• See the table

show tables;

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View table structure

desc winton

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Build table

create table t1( id int not null primary key, name char(20) not null );

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grammar create table The name of the table ( Field name Field name type Field descriptors , Field name Field type Field descriptors );

Delete table

drop table test;

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grammar ：drop table The name of the table ;

Modify table

Add fields

alter table t1 add(score int not null);

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grammar ：alter table Demonstrative scale add( Field name type The descriptor );

Remove field

alter table t1 drop column score;

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grammar ：alter table Table name drop colunm Field name ,drop colunm Field name ;

Change field

alter table t1 change name score int not null;

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grammar ：alter table Table name change Old field name new field name New field descriptor

Insert

Full field insertion

insert into winton values(001,'zww'),(002,'rs');

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grammar ：insert into Table name values( Field 1 value , Field 2 value ,……),( Field 1 value , Field 2 value ,……);

Insert individual fields

insert into winton(id) values(004);

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View the inserted results , As shown in the figure above .

grammar ：insert inton Table name ( Field name ) values( It's worth one ),( It's worth two );

Common query

Single table full field query

select * from t1;

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grammar ：select * from Table name ;

Query individual fields in a single table

select id from t1;

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grammar ：select Field one , Field 2 from Table name ;

Multi-table query

select t1.id,t1.score,winton.name from t1,winton;

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grammar ：select Table 1 field , Table II fields , Table III fields ,…… from Table 1 , Table two , Table 3 ,……

Conditions of the query

Single table condition query

select * from t1 where socre>90;

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grammar ：select Field 1, Field 2 from Table name where Conditions ;

Multi table conditional query

select t1.id,t1.score,winton.name from t1,winton where t1.id=winton.id;

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grammar ：select Table 1 field , Table II fields from Table 1 , Table two where Conditions ;

nested queries

select name from winton where id=(select id from t1 where score=90);

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grammar ：select Field one , Field 2 …… from Table name where Conditions （ Inquire about ）;

And query

(select id from t1 )union(select id from winton);

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I'd like to make an inquiry

select id from t1 where id in (select id from winton);

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Delete

delete from winton where id=4;

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grammar ：delete from Table name where Conditions ;

to update

update t1 set score=69 where id=2;

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grammar ：update Table name set Changed field name = value where Conditions ;

Common functions

Sum up

select sum(score) from t1;

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notes ：sum( Field ) Invalid for string and time

averaging

select avg(score) from t1; 

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notes ：avg( Field ) Invalid for string and time

Count

select count(*) from t1;

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notes ：count( Field name ) It doesn't contain NULL;

For maximum

select max(name) from winton;

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notes ：max(colunm) Returns the highest alphabetical order , Returns the highest value

For the minimum

select min(name) from winton;

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notes ：min(colunm) Returns the lowest value in alphabetical order , Returns the minimum value of the value

Common modifiers

distinct The value in the field is unique

select distinct name from winton;

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limit The number of query results is limited

select * from winton limit 2;

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order by Sort

select * from winton order by name;

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notes ： The default is ascending

desc Descending

slelect * from winton order by name desc;

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asc Ascending

select * from winton order by name asc;

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group by grouping

select name from winton group by name;

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Indexes

Create a normal index

create index wintonIndex on winton (name);

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grammar ：create index The index name on Table name ( Field one , Field 2 ,……);

Create unique index

create unique index wintonIndex on winton (id);

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grammar ：create unique index Index name on Table name ( Field one , Field 2 ,……); ps:unique index The data in the column is required to be unique , No repetition .

Remove index

drop index wintonIndex on winton;

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grammar : drop index Index name on Table name ;

ending

Okay , Basically, what you can remember is worth so much , Are the most basic , Some of the most commonly used .

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