2018/08/16--mysql数据库

SELECT cust_id,order_num FROM orders WHERE order_date='2005-09-01';

SELECT cust_id,order_num FROM orders WHERE order_date='2018-08-16';

SELECT cust_id,order_num FROM orders WHERE Date(order_date)='2018-08-16';

SELECT cust_id,order_num FROM orders WHERE Date(order_date) BETWEEN '2005-09-01' AND '2005-09-30';

SELECT cust_id,order_num FROM orders WHERE Year(order_date)=2005 AND Month(order_date)=9;

SELECT AVG(prod_price) FROM products;

SELECT AVG(prod_price) FROM products WHERE vend_id=1003;

SELECT COUNT(*) AS num_cust FROM customers;

SELECT COUNT(cust_email) AS num_cust FROM customers;

关于mysql的日期格式

mysql的日期格式为:yyyy-mm-dd

支持两位数字的年份，00-99，其中 00-69 表示2000-2069，70-99表示1970-1999

关于mysql的时间和日期处理函数

Date()：返回日期时间的日期部分

Year()：返回日期中的年份

Month()：返回日期中的月份

Time()：返回日期时间的时间部分

关于mysql常用的数值处理函数

 abs()：返回绝对值

Mod()：返回除后的余数

Pi()：返回圆周率

Rand()：返回随机数

DESCRIBE orders;

Field	Type	Null	Key	Default	Extra
order_num	int(11)	NO	PRI	NULL	auto_increment
order_date	datetime	NO		NULL
cust_id	int(11)	NO	MUL	NULL

SELECT * FROM orders;

order_num	order_date	cust_id
20005	2005-09-01 00:00:00	10001
20006	2005-09-12 00:00:00	10003
20007	2005-09-30 00:00:00	10004
20008	2005-10-03 00:00:00	10005
20009	2018-08-16 16:57:02	10001

SELECT cust_id,order_num FROM orders WHERE order_date='2005-09-01';

cust_id	order_num
10001	20005

SELECT cust_id,order_num FROM orders WHERE order_date='2018-08-16';

Empty set.

SELECT cust_id,order_num FROM orders WHERE Date(order_date)='2018-08-16';

cust_id	order_num
10001	20009

SELECT cust_id,order_num FROM orders WHERE order_date BETWEEN '2005-09-01' AND '2005-09-30';

cust_id	order_num
10001	20005
10003	20006
10004	20007

SELECT cust_id,order_num FROM orders WHERE Year(order_date)=2005 AND Month(order_date)=9;

cust_id	order_num
10001	20005
10003	20006
10004	20007

 关于mysql的聚集函数

AVG()：返回平均值

COUNT()： 返回列的行数

MAX() ：返回列的最大值

MIN() ：返回列的最小值

SUM()：返回列的和