Basic SQL operations in tidb

Successful deployment TiDB After cluster , You can do it in TiDB In the implementation of SQL Statement . because TiDB compatible MySQL, You can use MySQL Client connection TiDB, also Most of the time Can be executed directly MySQL sentence .

SQL Is a declarative language , It is a way for database users to interact with the database . It is more like a natural language , It seems that we are talking with the database in English . This document describes the basic SQL operation . complete SQL Statement list , See  TiDB SQL Grammar explanation .

classification

SQL Languages are usually divided into the following according to their functions 4 Parts of ：

• DDL (Data Definition Language)： Data definition language , Used to define database objects , Including the library 、 surface 、 Views and indexes, etc .

• DML (Data Manipulation Language)： Data operation language , Used to operate business-related records .

• DQL (Data Query Language)： Data query language , Used to query records filtered by criteria .

• DCL (Data Control Language)： Data control language , Used to define access rights and security levels .

frequently-used DDL Function is object （ As shown in the table 、 Index, etc. ） The creation of 、 Property modification and deletion , The corresponding commands are CREATE、ALTER and DROP.

see 、 Create and delete databases

TiDB In context Database Or database , It can be considered as a collection of objects such as tables and indexes .

Use  SHOW DATABASES  Statement to view the list of databases in the system ：

SHOW DATABASES;

Use the name  mysql  The database of ：

USE mysql;

Use  SHOW TABLES  Statement to view all tables in the database . for example ：

SHOW TABLES FROM mysql;

Use  CREATE DATABASE  Statement create database . The grammar is as follows ：

CREATE DATABASE db_name [options];

for example , To create a  samp_db  The database of , You can use the following statements ：

CREATE DATABASE IF NOT EXISTS samp_db;

add to  IF NOT EXISTS  Prevents errors .

Use  DROP DATABASE  Statement to delete the database . for example ：

DROP DATABASE samp_db;

establish 、 View and delete tables

Use  CREATE TABLE  Statement create table . The grammar is as follows ：

CREATE TABLE table_name column_name data_type constraint;

for example , To create a  person  Table of , Including numbering 、 name 、 Birthday and other fields , You can use the following statements ：

CREATE TABLE person ( id INT(11), name VARCHAR(255), birthday DATE );

Use  SHOW CREATE  Statement view table creation statement , namely DDL. for example ：

SHOW CREATE TABLE person;

Use  DROP TABLE  Statement delete table . for example ：

DROP TABLE person;

establish 、 View and delete indexes

Indexes are often used to speed up queries on indexed columns . For columns with non unique values , You can use  CREATE INDEX  or  ALTER TABLE  Statement to create a normal index . for example ：

CREATE INDEX person_id ON person (id);

perhaps ：

ALTER TABLE person ADD INDEX person_id (id);

For columns with unique values , You can create a unique index . for example ：

CREATE UNIQUE INDEX person_unique_id ON person (id);

perhaps ：

ALTER TABLE person ADD UNIQUE person_unique_id (id);

Use  SHOW INDEX  Statement to view all indexes in the table ：

SHOW INDEX FROM person;

Use  ALTER TABLE  or  DROP INDEX  Statement to delete index . And  CREATE INDEX  Statements like ,DROP INDEX  You can also embed  ALTER TABLE  sentence . for example ：

DROP INDEX person_id ON person;

ALTER TABLE person DROP INDEX person_unique_id;

Be careful ：DDL Operations are not transactions , In execution DDL when , There is no need to correspond to COMMIT sentence .

frequently-used DML The function is to add table records 、 Modification and deletion , The corresponding commands are INSERT、UPDATE and DELETE.

Addition, deletion and modification of records

Use  INSERT  Statement to insert a table record into a table . for example ：

INSERT INTO person VALUES(1,'tom','20170912');

Use  INSERT  Statement to insert a table record containing some field data into the table . for example ：

INSERT INTO person(id,name) VALUES('2','bob');

Use  UPDATE  Statement to modify some field data of a table record into a table . for example ：

UPDATE person SET birthday='20180808' WHERE id=2;

Use  DELETE  Statement to delete part of a table record . for example ：

DELETE FROM person WHERE id=2;

Be careful ：UPDATE and DELETE Operation without WHERE The filter condition is to operate the whole table .

DQL Data query language is to retrieve the desired data row from one or more tables , It is usually the core content of business development .

Query data

Use  SELECT  Statement to retrieve data in a table . for example ：

SELECT * FROM person;

stay SELECT Add the column name to be queried . for example ：

SELECT name FROM person;

+------+ | name | +------+ | tom | +------+ 1 rows in set (0.00 sec)

Use WHERE Clause , Filter all records to see if they meet the criteria before returning . for example ：

SELECT * FROM person WHERE id<5;

frequently-used DCL The function is to create or delete users , And the management of user rights .

establish 、 Authorize and delete users

Use  CREATE USER  Statement to create a user  tiuser, The password for  123456：

CREATE USER 'tiuser'@'localhost' IDENTIFIED BY '123456';

Authorized user  tiuser  Searchable database  samp_db  Table in ：

GRANT SELECT ON samp_db.* TO 'tiuser'@'localhost';

Query the user  tiuser  Authority ：

SHOW GRANTS for [email protected];

Delete user  tiuser：

DROP USER 'tiuser'@'localhost';