net start mysqlmysql -uroot -pshow databasesuse 数据库名how tables--------------------------------------------------------------------------select goods_id ,goods_name ,shop_price+1,market_price,market_price-shop_price from goods;select * from goods where goods_id = 32;select goods_id,goods_name,cat_id from goods where cat_id <> 32;//不等于select goods_id,goods_name,cat_id from goods where cat_id > 32;//不等于select goods_id,goods_name,cat_id from goods where cat_id <= 32 and cat_id >= 2;//不等于select goods_id,cat_id from goods where cat_id = 4 or cat_id =11;//或者select goods_id,cat_id from goods where cat_id  in (4,11);//4，11选一个select goods_id,cat_id from goods where cat_id  between  4 and 11;//4--11之间select goods_id,cat_id from goods where cat_id  not in (4,11);//不是4，11select click_count ,cat_id,shop_price from goods where cat_id = 3 and (shop_price < 1000 or shop_price > 3000) and click_count>5;  //and优先级高于orselect goods_name from goods where goods_name like '诺基亚%';//%是任意字符select goods_name from goods where goods_name like '诺基亚___';//___3个下划线是3个字符select cat_id,sum(goods_number*shop_price) as k from goods group by cat_id having k>20000(5个聚合函数,sum,avg,max,min,count与group综合运用) select cat_id,max(shop_price) from ecs_goods  group by cat_id;select goods_id,cat_id,goods_name,shop_price  from ecs_goods where cat_id=3 and shop_price>1000 and shop_price <3000 and click_count>5 and goods_name like '诺基亚%';select goods_id,cat_id,goods_name,shop_price  from ecs_goods where shop_price between 1000 and 3000 and cat_id=3  and click_count>5 and goods_name like '诺基亚%';select goods_id,cat_id,goods_name,shop_price  from ecs_goods where goods_name like '诺基亚N__';select goods_id,cat_id,goods_name,shop_price from ecs_goos where goods_name not like '诺基亚%';select goods_id,cat_id,goods_name,shop_price,click_count from ecs_goods where cat_id=3 and (shop_price <1000 or shop_price>3000) and click_count>5;select goods_id,cat_id,goods_name,shop_price  from ecs_goods     where cat_id not in (3,11);取出100<=价格<=500的商品(不许用and)select goods_id,cat_id,goods_name,shop_price  from ecs_goods where shop_price between 100 and 500;1.15 一道面试题，有如下表和数组，把num值处于[20,29]之间,改为20，num值处于[30,39]之间的,改为30select floor(num/10)*10 from mian;updata mian set num=floor(num/10)*10;update mian set num=floor(num/10)*10 where num between 20 and 29;1.16 练习题:把good表中商品名为'诺基亚xxxx'的商品,改为'HTCxxxx',update goods set goods_name = concat('htc',substring(goods_name,4))  where goods_name like '诺基亚%';------------------------------------------------------------------------------------------------------NULL ： insert into user values (1,null,99,'rr');//Column 'name' cannot be nullmysql> create table tmp(    -> id int,    -> name varchar(20)    -> ) charset utf8 engine myisam;insert into tmp values (1,'ll'),(2,'ffff'),(3,null);mysql> select * from tmp;+----+------+| id | name |+----+------+|  1 | ll   ||  1 | ll   ||  2 | ffff ||  3 | NULL |+----+------+4 rows in setmysql> select * from tmp where name = null;Empty setmysql> select * from tmp where name != null;Empty setmysql> select * from tmp where name is null;+----+------+| id | name |+----+------+|  3 | NULL |+----+------+1 row in setmysql> select * from tmp where name is not null;+----+------+| id | name |+----+------+|  1 | ll   ||  1 | ll   ||  2 | ffff |+----+------+3 rows in setmysql> desc tmp;//查看表的结构: +-------+-------------+------+-----+---------+-------+| Field | Type        | Null | Key | Default | Extra |+-------+-------------+------+-----+---------+-------+| id    | int(11)     | YES  |     | NULL    |       || name  | varchar(20) | YES  |     | NULL    |       |+-------+-------------+------+-----+---------+-------+2 rows in setmysql> show create table  tmp;//查看表的创建过程: +-------+---------------+| Table | Create Table                                                                                                          |+-------+--------------+| tmp   | CREATE TABLE `tmp` (  `id` int(11) DEFAULT NULL,  `name` varchar(20) DEFAULT NULL) ENGINE=MyISAM DEFAULT CHARSET=utf8 |+-------+------------+1 row in set----------------------------------------------------------------------------------------------------------mysql> select avg(shop_price) from goods;mysql> select count(*) from goods;mysql> select sum(goods_number*shop_price) from goods;//求2列相乘后的和mysql> select avg(shop_price) ,cat_id from goods group by cat_id;//先根据cat_id分组，再求每组的平均值。+-----------------+--------+| avg(shop_price) | cat_id |+-----------------+--------+| 823.330000      |      2 || 1746.066667     |      3 || 2297.000000     |      4 || 3700.000000     |      5 || 75.333333       |      8 || 31.000000       |     11 || 33.500000       |     13 || 54.000000       |     14 || 70.000000       |     15 |+-----------------+--------+9 rows in setmysql>  select count(*) ,cat_id from goods group by cat_id;//根据cat_id分组，再查每组的数量。+----------+--------+| count(*) | cat_id |+----------+--------+|        1 |      2 ||       15 |      3 ||        3 |      4 ||        1 |      5 ||        3 |      8 ||        2 |     11 ||        2 |     13 ||        2 |     14 ||        2 |     15 |+----------+--------+9 rows in setmysql>  select max(shop_price) ,cat_id from goods group by cat_id;+-----------------+--------+| max(shop_price) | cat_id |+-----------------+--------+| 823.33          |      2 || 5999            |      3 || 2878            |      4 || 3700            |      5 || 100             |      8 || 42              |     11 || 48              |     13 || 90              |     14 || 95              |     15 |+-----------------+--------+9 rows in setmysql> select goods_id, goods_name, market_price - shop_price from goods;+----------+---------------------------+---------------------------+| goods_id | goods_name                | market_price - shop_price |+----------+---------------------------+---------------------------+|        1 | kd876                     | 277.6                     ||        4 | htcn85原装充电器          | 11.6                      |+----------+---------------------------+---------------------------+31 rows in set-------------------------------------------------------------------------------------------------------having对结果集操作： where---group by---having---order by ---limit数据库数据保存在goods.MYD文件里面，select xxx from goods where cat_id=3 查询的临时结果集result放在内存中，where是针对表起作用，select (market_price - shop_price) as less中的less在内存结果集中不在表中，所以对表中where less > 700不起作用，想好针对结果集发挥作用只能用having了，mysql> select goods_id, goods_name ,(market_price - shop_price) as less from goods [where 1] having less > 700;+----------+----------------+--------+| goods_id | goods_name     | less   |+----------+----------------+--------+|       22 | 多普达touch hd | 1199.8 ||       23 | htcn96         | 740    |+----------+----------------+--------+2 rows in set所以where不能写在having后面，因为只有where从表中查询出结果集后，然后用having对结果集操作。有如下表及数据+------+---------+-------+| name | subject | score |+------+---------+-------+| 张三 | 数学    |    90 || 张三 | 语文    |    50 || 张三 | 地理    |    40 || 李四 | 语文    |    55 || 李四 | 政治    |    45 || 王五 | 政治    |    30 |+------+---------+-------+   要求:查询出2门及2门以上不及格者的平均成绩drop table tmp;mysql> select count(score<=60) as num from temp;+-----+| num |+-----+|   6 |+-----+1 row in setmysql> select count(score<=60) as num from temp group by name;+-----+| num |+-----+|   3 ||   1 ||   2 |+-----+3 rows in setmysql>  select name, count(score<=60) as num, avg(score) from temp where 1 group by name having num>=2;+------+-----+------------+| name | num | avg(score) |+------+-----+------------+| 三   |   3 | 60.0000    || 四   |   2 | 30.0000    |+------+-----+------------+-------------------------------------------------------------------------------------------------------order by：在内存中排序mysql> select * from goods order by shop_price , cat_id;取出点击量前三名到前5名的商品select goods_id,goods_name,click_count from ecs_goods order by click_count desc limit 2,5;//跳过2个从第三个开始，取出5个，where 子查询：查询出最新的商品(以商品编号goods_id最大为最新,用子查询实现)select goods_id,goods_name from goods where goods_id =(select max(goods_id) from ecs_goods);查询出每一个cat_id下最新的商品(先查询每个cat_id下goods_id的最大值)mysql> select goods_id,cat_id from goods where goods_id in (select max(goods_id) from goods group by cat_id) order by cat_id asc;from子查询：mysql> select goods_id from (select goods_id,goods_name from goods order by goods_id asc, goods_name desc) as temp where goods_id between 10 and 13;+----------+| goods_id |+----------+|       10 ||       11 ||       12 ||       13 |+----------+mysql> select goods_id as gid from (select goods_id,goods_name from goods  order by goods_id asc, goods_name desc) as temp where goods_id between 10 and 13 order by gid desc limit 1,2;//有的地方要加as不加as不行, 空格作为分隔符逗号作为连接符。+-----+| gid |+-----+|  12 ||  11 |+-----+exists型子查询：查出所有有商品的栏目cart_idselect * from category where exists (select * from goods where goods.cat_id=category.cat_id);mysql> select goods.cat_id,category.cat_id from goods,category where goods.cat_id = category.cat_id limit 1,5;//2个表查询+--------+--------+| cat_id | cat_id |+--------+--------+|      8 |      8 ||      8 |      8 ||     11 |     11 ||     11 |     11 ||      8 |      8 |+--------+--------+-----------------------------------------------------------------------------------------------------------------1+N模式查询：------------------------------------------------------------------------------------------------------------------连接查询：左连接，left join on，table A left join table B on tableA.col1 = tableB.col2 ; 连接完了之后就成了一个大表格(from boy left join girl on boy.hid=girl.hid就是一张大表，后面的写法跟一张表一样写法，)。on是表连接的条件。mysql> select * from girl;   mysql> select * from boy;+-----+--------+        +-----+--------+| hid | gname  |        | hid | bname  |+-----+--------+        +-----+--------+| B   | 小龙女 |        | A   | 屌丝   || C   | 张柏芝 |        | B   | 杨过   || D   | mv     |        | C   | 陈冠希 || E   | no     |        | D   | yw     |+-----+--------+        +-----+--------+mysql> select boy.hid,boy.bname,girl.hid,girl.gname from boy left join girl on boy.hid=girl.hid;//左边的表全部列出来，进行右边表的匹配，匹配不上就没有，+-----+--------+------+--------+| hid | bname  | hid  | gname  |+-----+--------+------+--------+| B   | 杨过   | B    | 小龙女 || C   | 陈冠希 | C    | 张柏芝 || D   | yw     | D    | mv     || A   | 屌丝   | NULL | NULL   |+-----+--------+------+--------+mysql> select boy.hid,boy.bname,girl.hid,girl.gname from boy right join girl on boy.hid=girl.hid;//右边的表全部列出来，进行左边表的匹配，匹配不上就没有，+------+--------+-----+--------+| hid  | bname  | hid | gname  |+------+--------+-----+--------+| B    | 杨过   | B   | 小龙女 || C    | 陈冠希 | C   | 张柏芝 || D    | yw     | D   | mv     || NULL | NULL   | E   | no     |+------+--------+-----+--------+mysql> select boy.hid,boy.bname,girl.hid,girl.gname from boy inner join girl on boy.hid=girl.hid;//剔除没有匹配上的，inner join是求交集，求并集是外连接，mysql没有外连接，oracle和sqlsercver有外连接。+-----+--------+-----+--------+| hid | bname  | hid | gname  |+-----+--------+-----+--------+| B   | 杨过   | B   | 小龙女 || C   | 陈冠希 | C   | 张柏芝 || D   | yw     | D   | mv     |+-----+--------+-----+--------+select goods_name,cat_name,shop_price from goods left join category on goods.cat_id=category.cat_id //大表，where goods.cat_id = 4;mysql> select * from boygirl;+--------+--------+| boygid | byname |+--------+--------+| A      | aaa    || B      | bbb    || C      | ccc    || D      | ddd    |+--------+--------+mysql> select * from boy left join girl on gid=bid;+-----+--------+------+--------+| bid | bname  | gid  | gname  |+-----+--------+------+--------+| B   | 杨过   | B    | 小龙女 || C   | 陈冠希 | C    | 张柏芝 || D   | yw     | D    | mv     || A   | 屌丝   | NULL | NULL   |+-----+--------+------+--------+mysql> select * from boy left join girl on gid=bid     //left join成一张大表，这张大表再去右连接，right join boygirl on boygid=gid;+------+--------+------+--------+--------+--------+| bid  | bname  | gid  | gname  | boygid | byname |+------+--------+------+--------+--------+--------+| B    | 杨过   | B    | 小龙女 | B      | bbb    || C    | 陈冠希 | C    | 张柏芝 | C      | ccc    || D    | yw     | D    | mv     | D      | ddd    || NULL | NULL   | NULL | NULL   | A      | aaa    |+------+--------+------+--------+--------+--------+mysql> select * from boy left join girl as tmp on gid=bid  right join boygirl on boygirl.boygid=tmp.gid;//取boy left join girl大表的别名为tmp,+------+--------+------+--------+--------+--------+| bid  | bname  | gid  | gname  | boygid | byname |+------+--------+------+--------+--------+--------+| B    | 杨过   | B    | 小龙女 | B      | bbb    || C    | 陈冠希 | C    | 张柏芝 | C      | ccc    || D    | yw     | D    | mv     | D      | ddd    || NULL | NULL   | NULL | NULL   | A      | aaa    |+------+--------+------+--------+--------+--------+mysql> select * from boy left join girl as t1 on boy.bid = t1.gid;//t1为girl的别名。+-----+--------+------+--------+| bid | bname  | gid  | gname  |+-----+--------+------+--------+| B   | 杨过   | B    | 小龙女 || C   | 陈冠希 | C    | 张柏芝 || D   | yw     | D    | mv     || A   | 屌丝   | NULL | NULL   |+-----+--------+------+--------+select gc.goods_name,gc.cat_name,gb.brand_name from goods left join category as gcon goods.cat_id=category.cat_idleft join brand as gbon goods.brand_id=brand.brand_idwhere goods.cat_id = 4;----------------------------------------------------------------------------------------------------union查询：把多个sql的查询结果合并成一个结果集。必须满足表的列数相同。字段不同都可以，以前面表格的字段为新字段。完全相同的行将会被合并，union all就不会合并完全相同的行。mysql> select * from study_new union all select * from m;+----+----------+-------+-----+------------+| id | username | class | sex | addtime    |+----+----------+-------+-----+------------+|  1 | 小王     |     1 | 男  | 0          ||  2 | 小四     |     2 | 女  | 0          ||  1 | 1        |     2 | 2:0 | 2006-05-21 ||  2 | 2        |     3 | 1:2 | 2006-06-21 ||  3 | 3        |     1 | 2:5 | 2006-06-25 ||  4 | 2        |     1 | 3:2 | 2006-07-21 |+----+----------+-------+-----+------------+

一、数学函数abs(x)   返回x的绝对值bin(x)   返回x的二进制（oct返回八进制，hex返回十六进制）ceiling(x)   返回大于x的最小整数值exp(x)   返回值e（自然对数的底）的x次方floor(x)   返回小于x的最大整数值greatest(x1,x2,...,xn)返回集合中最大的值least(x1,x2,...,xn)      返回集合中最小的值ln(x)                    返回x的自然对数log(x,y)返回x的以y为底的对数mod(x,y)                 返回x/y的模（余数）pi()返回pi的值（圆周率）rand()返回０到１内的随机值,可以通过提供一个参数(种子)使rand()随机数生成器生成一个指定的值。round(x,y)返回参数x的四舍五入的有y位小数的值sign(x) 返回代表数字x的符号的值sqrt(x) 返回一个数的平方根truncate(x,y)            返回数字x截短为y位小数的结果二、聚合函数(常用于group by从句的select查询中)avg(col)返回指定列的平均值count(col)返回指定列中非null值的个数min(col)返回指定列的最小值max(col)返回指定列的最大值sum(col)返回指定列的所有值之和group_concat(col) 返回由属于一组的列值连接组合而成的结果三、字符串函数ascii(char)返回字符的ascii码值bit_length(str)返回字符串的比特长度concat(s1,s2...,sn)将s1,s2...,sn连接成字符串concat_ws(sep,s1,s2...,sn)将s1,s2...,sn连接成字符串，并用sep字符间隔insert(str,x,y,instr) 将字符串str从第x位置开始，y个字符长的子串替换为字符串instr，返回结果find_in_set(str,list)分析逗号分隔的list列表，如果发现str，返回str在list中的位置lcase(str)或lower(str) 返回将字符串str中所有字符改变为小写后的结果left(str,x)返回字符串str中最左边的x个字符length(s)返回字符串str中的字符数ltrim(str) 从字符串str中切掉开头的空格position(substr,str) 返回子串substr在字符串str中第一次出现的位置quote(str) 用反斜杠转义str中的单引号repeat(str,srchstr,rplcstr)返回字符串str重复x次的结果reverse(str) 返回颠倒字符串str的结果right(str,x) 返回字符串str中最右边的x个字符rtrim(str) 返回字符串str尾部的空格strcmp(s1,s2)比较字符串s1和s2trim(str)去除字符串首部和尾部的所有空格ucase(str)或upper(str) 返回将字符串str中所有字符转变为大写后的结果四、日期和时间函数curdate()或current_date() 返回当前的日期curtime()或current_time() 返回当前的时间date_add(date,interval int keyword)返回日期date加上间隔时间int的结果(int必须按照关键字进行格式化),如：selectdate_add(current_date,interval 6 month);date_format(date,fmt)  依照指定的fmt格式格式化日期date值date_sub(date,interval int keyword)返回日期date加上间隔时间int的结果(int必须按照关键字进行格式化),如：selectdate_sub(current_date,interval 6 month);dayofweek(date)   返回date所代表的一星期中的第几天(1~7)dayofmonth(date)  返回date是一个月的第几天(1~31)dayofyear(date)   返回date是一年的第几天(1~366)dayname(date)   返回date的星期名，如：select dayname(current_date);from_unixtime(ts,fmt)  根据指定的fmt格式，格式化unix时间戳tshour(time)   返回time的小时值(0~23)minute(time)   返回time的分钟值(0~59)month(date)   返回date的月份值(1~12)monthname(date)   返回date的月份名，如：select monthname(current_date);now()    返回当前的日期和时间quarter(date)   返回date在一年中的季度(1~4)，如select quarter(current_date);week(date)   返回日期date为一年中第几周(0~53)year(date)   返回日期date的年份(1000~9999)一些示例：获取当前系统时间：select from_unixtime(unix_timestamp());select extract(year_month from current_date);select extract(day_second from current_date);select extract(hour_minute from current_date);返回两个日期值之间的差值(月数)：select period_diff(200302,199802);在mysql中计算年龄：select date_format(from_days(to_days(now())-to_days(birthday)),'%y')+0 as age from employee;这样，如果brithday是未来的年月日的话，计算结果为0。下面的sql语句计算员工的绝对年龄，即当birthday是未来的日期时，将得到负值。select date_format(now(), '%y') - date_format(birthday, '%y') -(date_format(now(), '00-%m-%d') 
     
      100,'true','false');if()函数在只有两种可能结果时才适合使用。然而，在现实世界中，我们可能发现在条件测试中会需要多个分支。在这种情况下，mysql提供了case函数，它和php及perl语言的switch-case条件例程一样。case函数的格式有些复杂，通常如下所示：case [expression to be evaluated]when [val 1] then [result 1]when [val 2] then [result 2]when [val 3] then [result 3]......when [val n] then [result n]else [default result]end这里，第一个参数是要被判断的值或表达式，接下来的是一系列的when-then块，每一块的第一个参数指定要比较的值，如果为真，就返回结果。所有的when-then块将以else块结束，当end结束了所有外部的case块时，如果前面的每一个块都不匹配就会返回else块指定的默认结果。如果没有指定else块，而且所有的when-then比较都不是真，mysql将会返回null。case函数还有另外一种句法，有时使用起来非常方便，如下：casewhen [conditional test 1] then [result 1]when [conditional test 2] then [result 2]else [default result]end这种条件下，返回的结果取决于相应的条件测试是否为真。示例：mysql>select case 'green'     when 'red' then 'stop'     when 'green' then 'go' end;select case 9 when 1 then 'a' when 2 then 'b' else 'n/a' end;select case when (2+2)=4 then 'ok' when(2+2)<>4 then 'not ok' end asstatus;select name,if((isactive = 1),'已激活','未激活') as result fromuserlogininfo;select fname,lname,(math+sci+lit) as total,case when (math+sci+lit) < 50 then 'd'when (math+sci+lit) between 50 and 150 then 'c'when (math+sci+lit) between 151 and 250 then 'b'else 'a' endas grade from marks;select if(encrypt('sue','ts')=upass,'allow','deny') as loginresultfrom users where uname = 'sue';#一个登陆验证七、格式化函数date_format(date,fmt)  依照字符串fmt格式化日期date值format(x,y)   把x格式化为以逗号隔开的数字序列，y是结果的小数位数inet_aton(ip)   返回ip地址的数字表示inet_ntoa(num)   返回数字所代表的ip地址time_format(time,fmt)  依照字符串fmt格式化时间time值其中最简单的是format()函数，它可以把大的数值格式化为以逗号间隔的易读的序列。示例：select format(34234.34323432,3);select date_format(now(),'%w,%d %m %y %r');select date_format(now(),'%y-%m-%d');select date_format(19990330,'%y-%m-%d');select date_format(now(),'%h:%i %p');select inet_aton('10.122.89.47');select inet_ntoa(175790383);八、类型转化函数为了进行数据类型转化，mysql提供了cast()函数，它可以把一个值转化为指定的数据类型。类型有：binary,char,date,time,datetime,signed,unsigned示例：select cast(now() as signed integer),curdate()+0;select 'f'=binary 'f','f'=cast('f' as binary);九、系统信息函数database()   返回当前数据库名benchmark(count,expr)  将表达式expr重复运行count次connection_id()   返回当前客户的连接idfound_rows()   返回最后一个select查询进行检索的总行数user()或system_user()  返回当前登陆用户名version()   返回mysql服务器的版本示例：select database(),version(),user();selectbenchmark(9999999,log(rand()*pi()));#该例中,mysql计算log(rand()*pi())表达式9999999次。