常用SQL语句总结

Posted 2021-11-22 Data+Science+Insight

常用SQL语句总结

常用SQL语句总结：

创建数据库:CREATE DATABASE database-name

删除数据库：drop database dbname

创建数据表：create table tabname(col1 type1 [not null] [primary key],col2 type2 [not null],..)

删除表：drop table tabname 

为表增加数据列：Alter table tabname add column col type

为表添加主键：Alter table tabname add primary key(col) 

删除数据表主键： Alter table tabname drop primary key(col)

为数据表创建索引：create [unique] index idxname on tabname(col….)

删除数据表索引：drop index idxname

为数据表创建视图：create view viewname as select statement

删除数据表的视图：drop view viewname

选择：select * from table1 where 范围
插入：insert into table1(field1,field2) values(value1,value2)
删除：delete from table1 where 

范围更新：update table1 set field1=value1 where 范围
查找：select * from table1 where field1 like ’%value1%’ ---like的语法很精妙，查资料!
排序：select * from table1 order by field1,field2 [desc]
总数：select count as totalcount from table1
求和：select sum(field1) as sumvalue from table1
平均：select avg(field1) as avgvalue from table1
最大：select max(field1) as maxvalue from table1
最小：select min(field1) as minvalue from table1

左连接：

SELECT Developers.Name, Customer_orders.ID FROM Developers LEFT JOIN Customer_orders ON Developers.ID = Customer_orders.customer_id ORDER BY Developers.Name;

右连接：

SELECT Customer_orders.ID, Employees.Last_name, Employees.First_name FROM Customer_orders RIGHT JOIN Employees ON Customer_orders.employee_id = Employees.ID ORDER BY Customer_orders.ID;

全连接：

SELECT Customers.Name, Customer_orders.ID FROM Customers FULL OUTER JOIN Orders ON Customers.ID=Customer_orders.customer_id ORDER BY Customers.Name;

like匹配：SELECT * FROM users WHERE email LIKE '%gmail%';

排序（order）:SELECT * FROM users ORDER BY email DESC;

唯一值(distinct):SELECT DISTINCT City FROM Developers;

数据分组（group by）: SELECT COUNT(ID), City FROM Developers GROUP BY City;

存在检查（exists）:SELECT id, name FROM customers WHERE EXISTS (SELECT id FROM customer_orders WHERE customer_orders.customer_id = customers.id AND customers.city = "Rome");

参考：Most Used SQL Queries For Beginner

参考：sql常用语句汇总