sql从简单到高级

Posted 2020-10-03 学无止境

? 基本常用查询 
--select 
select * from student; 
--all 查询所有 
select all sex from student; 
--distinct 过滤重复 
select distinct sex from student; 
--count 统计 
select count(*) from student; 
select count(sex) from student; 
select count(distinct sex) from student; 
--top 取前N条记录 
select top 3 * from student; 
--alias column name 列重命名 
select id as 编号, name ‘名称‘, sex 性别 from student; 
--alias table name 表重命名 
select id, name, s.id, s.name from student s; 
--column 列运算 
select (age + id) col from student; 
select s.name + ‘-‘ + c.name from classes c, student s where s.cid = c.id; 
--where 条件 
select * from student where id = 2; 
select * from student where id > 7; 
select * from student where id < 3; 
select * from student where id <> 3; 
select * from student where id >= 3; 
select * from student where id <= 5; 
select * from student where id !> 3; 
select * from student where id !< 5; 
--and 并且 
select * from student where id > 2 and sex = 1; 
--or 或者 
select * from student where id = 2 or sex = 1; 
--between ... and ... 相当于并且 
select * from student where id between 2 and 5; 
select * from student where id not between 2 and 5; 
--like 模糊查询 
select * from student where name like ‘%a%‘; 
select * from student where name like ‘%[a][o]%‘; 
select * from student where name not like ‘%a%‘; 
select * from student where name like ‘ja%‘; 
select * from student where name not like ‘%[j,n]%‘; 
select * from student where name like ‘%[j,n,a]%‘; 
select * from student where name like ‘%[^ja,as,on]%‘; 
select * from student where name like ‘%[ja_on]%‘; 
--in 子查询 
select * from student where id in (1, 2); 
--not in 不在其中 
select * from student where id not in (1, 2); 
--is null 是空 
select * from student where age is null; 
--is not null 不为空 
select * from student where age is not null; 
--order by 排序 
select * from student order by name; 
select * from student order by name desc; 
select * from student order by name asc; 
--group by 分组 
按照年龄进行分组统计 
select count(age), age from student group by age; 
按照性别进行分组统计 
select count(*), sex from student group by sex; 
按照年龄和性别组合分组统计，并排序 
select count(*), sex from student group by sex, age order by age; 
按照性别分组，并且是id大于2的记录最后按照性别排序 
select count(*), sex from student where id > 2 group by sex order by sex; 
查询id大于2的数据，并完成运算后的结果进行分组和排序 
select count(*), (sex * id) new from student where id > 2 group by sex * id order by sex * id; 
--group by all 所有分组 
按照年龄分组，是所有的年龄 
select count(*), age from student group by all age; 
--having 分组过滤条件 
按照年龄分组，过滤年龄为空的数据，并且统计分组的条数和现实年龄信息 
select count(*), age from student group by age having age is not null; 
按照年龄和cid组合分组，过滤条件是cid大于1的记录 
select count(*), cid, sex from student group by cid, sex having cid > 1; 
按照年龄分组，过滤条件是分组后的记录条数大于等于2 
select count(*), age from student group by age having count(age) >= 2; 
按照cid和性别组合分组，过滤条件是cid大于1，cid的最大值大于2 
select count(*), cid, sex from student group by cid, sex having cid > 1 and max(cid) > 2; 
? 嵌套子查询 
子查询是一个嵌套在select、insert、update或delete语句或其他子查询中的查询。任何允许使用表达式的地方都可以使用子查询。子查询也称为内部查询或内部选择，而包含子查询的语句也成为外部查询或外部选择。 
# from (select … table)示例 
将一个table的查询结果当做一个新表进行查询 
select * from ( 
select id, name from student where sex = 1 
) t where t.id > 2; 
上面括号中的语句，就是子查询语句（内部查询）。在外面的是外部查询，其中外部查询可以包含以下语句： 
1、 包含常规选择列表组件的常规select查询 
2、 包含一个或多个表或视图名称的常规from语句 
3、 可选的where子句 
4、 可选的group by子句 
5、 可选的having子句 
# 示例 
查询班级信息，统计班级学生人生 
select *, (select count(*) from student where cid = classes.id) as num 
from classes order by num; 
# in, not in子句查询示例 
查询班级id大于小于的这些班级的学生信息 
select * from student where cid in ( 
select id from classes where id > 2 and id < 4 
); 
查询不是班的学生信息 
select * from student where cid not in ( 
select id from classes where name = ‘2班‘ 
) 
in、not in 后面的子句返回的结果必须是一列，这一列的结果将会作为查询条件对应前面的条件。如cid对应子句的id； 
# exists和not exists子句查询示例 
查询存在班级id为的学生信息 
select * from student where exists ( 
select * from classes where id = student.cid and id = 3 
); 
查询没有分配班级的学生信息 
select * from student where not exists ( 
select * from classes where id = student.cid 
); 
exists和not exists查询需要内部查询和外部查询进行一个关联的条件，如果没有这个条件将是查询到的所有信息。如：id等于student.id； 
# some、any、all子句查询示例 
查询班级的学生年龄大于班级的学生的年龄的信息 
select * from student where cid = 5 and age > all ( 
select age from student where cid = 3 
); 
select * from student where cid = 5 and age > any ( 
select age from student where cid = 3 
); 
select * from student where cid = 5 and age > some ( 
select age from student where cid = 3 
); 
? 聚合查询 
1、 distinct去掉重复数据 
select distinct sex from student; 
select count(sex), count(distinct sex) from student; 
2、 compute和compute by汇总查询 
对年龄大于的进行汇总 
select age from student 
where age > 20 order by age compute sum(age) by age; 
对年龄大于的按照性别进行分组汇总年龄信息 
select id, sex, age from student 
where age > 20 order by sex, age compute sum(age) by sex; 
按照年龄分组汇总 
select age from student 
where age > 20 order by age, id compute sum(age); 
按照年龄分组，年龄汇总，id找最大值 
select id, age from student 
where age > 20 order by age compute sum(age), max(id); 
compute进行汇总前面是查询的结果，后面一条结果集就是汇总的信息。compute子句中可以添加多个汇总表达式，可以添加的信息如下： 
a、 可选by关键字。它是每一列计算指定的行聚合 
b、 行聚合函数名称。包括sum、avg、min、max、count等 
c、 要对其执行聚合函数的列 
compute by适合做先分组后汇总的业务。compute by后面的列一定要是order by中出现的列。 
3、 cube汇总 
cube汇总和compute效果类似，但语法较简洁，而且返回的是一个结果集。 
select count(*), sex from student group by sex with cube; 
select count(*), age, sum(age) from student where age is not null group by age with cube; 
cube要结合group by语句完成分组汇总 
? 排序函数 
排序在很多地方需要用到，需要对查询结果进行排序并且给出序号。比如： 
1、 对某张表进行排序，序号需要递增不重复的 
2、 对学生的成绩进行排序，得出名次，名次可以并列，但名次的序号是连续递增的 
3、 在某些排序的情况下，需要跳空序号，虽然是并列 
基本语法 
排序函数 over([分组语句] 排序子句[desc][asc]) 
排序子句 order by 列名, 列名 
分组子句 partition by 分组列, 分组列 
# row_number函数 
根据排序子句给出递增连续序号 
按照名称排序的顺序递增 
select s.id, s.name, cid, c.name, row_number() over(order by c.name) as number 
from student s, classes c where cid = c.id; 
# rank函数函数 
根据排序子句给出递增的序号，但是存在并列并且跳空 
顺序递增 
select id, name, rank() over(order by cid) as rank from student; 
跳过相同递增 
select s.id, s.name, cid, c.name, rank() over(order by c.name) as rank 
from student s, classes c where cid = c.id; 
# dense_rank函数 
根据排序子句给出递增的序号，但是存在并列不跳空 
不跳过，直接递增 
select s.id, s.name, cid, c.name, dense_rank() over(order by c.name) as dense 
from student s, classes c where cid = c.id; 
# partition by分组子句 
可以完成对分组的数据进行增加排序，partition by可以与以上三个函数联合使用。 
利用partition by按照班级名称分组，学生id排序 
select s.id, s.name, cid, c.name, row_number() over(partition by c.name order by s.id) as rank 
from student s, classes c where cid = c.id; 
select s.id, s.name, cid, c.name, rank() over(partition by c.name order by s.id) as rank 
from student s, classes c where cid = c.id; 
select s.id, s.name, cid, c.name, dense_rank() over(partition by c.name order by s.id) as rank 
from student s, classes c where cid = c.id; 
# ntile平均排序函数 
将要排序的数据进行平分，然后按照等分排序。ntile中的参数代表分成多少等分。 
select s.id, s.name, cid, c.name, 
ntile(5) over(order by c.name) as ntile 
from student s, classes c where cid = c.id; 
? 集合运算 
操作两组查询结果，进行交集、并集、减集运算 
1、 union和union all进行并集运算 
--union 并集、不重复 
select id, name from student where name like ‘ja%‘ 
union 
select id, name from student where id = 4; 
--并集、重复 
select * from student where name like ‘ja%‘ 
union all 
select * from student; 
2、 intersect进行交集运算 
--交集（相同部分） 
select * from student where name like ‘ja%‘ 
intersect 
select * from student; 
3、 except进行减集运算 
--减集（除相同部分） 
select * from student where name like ‘ja%‘ 
except 
select * from student where name like ‘jas%‘; 
? 公式表表达式 
查询表的时候，有时候中间表需要重复使用，这些子查询被重复查询调用，不但效率低，而且可读性低，不利于理解。那么公式表表达式可以解决这个问题。 
我们可以将公式表表达式（CET）视为临时结果集，在select、insert、update、delete或是create view语句的执行范围内进行定义。 
--表达式 
with statNum(id, num) as 
( 
select cid, count(*) 
from student 
where id > 0 
group by cid 
) 
select id, num from statNum order by id; 
with statNum(id, num) as 
( 
select cid, count(*) 
from student 
where id > 0 
group by cid 
) 
select max(id), avg(num) from statNum; 
? 连接查询 
1、 简化连接查询 
--简化联接查询 
select s.id, s.name, c.id, c.name from student s, classes c where s.cid = c.id; 
2、 left join左连接 
--左连接 
select s.id, s.name, c.id, c.name from student s left join classes c on s.cid = c.id; 
3、 right join右连接 
--右连接 
select s.id, s.name, c.id, c.name from student s right join classes c on s.cid = c.id; 
4、 inner join内连接 
--内连接 
select s.id, s.name, c.id, c.name from student s inner join classes c on s.cid = c.id; 
--inner可以省略 
select s.id, s.name, c.id, c.name from student s join classes c on s.cid = c.id; 
5、 cross join交叉连接 
--交叉联接查询，结果是一个笛卡儿乘积 
select s.id, s.name, c.id, c.name from student s cross join classes c 
--where s.cid = c.id; 
6、 自连接（同一张表进行连接查询） 
--自连接 
select distinct s.* from student s, student s1 where s.id <> s1.id and s.sex = s1.sex; 
? 函数 
1、 聚合函数 
max最大值、min最小值、count统计、avg平均值、sum求和、var求方差 
select 
max(age) max_age, 
min(age) min_age, 
count(age) count_age, 
avg(age) avg_age, 
sum(age) sum_age, 
var(age) var_age 
from student; 
2、 日期时间函数 
select dateAdd(day, 3, getDate());--加天 
select dateAdd(year, 3, getDate());--加年 
select dateAdd(hour, 3, getDate());--加小时 
--返回跨两个指定日期的日期边界数和时间边界数 
select dateDiff(day, ‘2011-06-20‘, getDate()); 
--相差秒数 
select dateDiff(second, ‘2011-06-22 11:00:00‘, getDate()); 
--相差小时数 
select dateDiff(hour, ‘2011-06-22 10:00:00‘, getDate()); 
select dateName(month, getDate());--当前月份 
select dateName(minute, getDate());--当前分钟 
select dateName(weekday, getDate());--当前星期 
select datePart(month, getDate());--当前月份 
select datePart(weekday, getDate());--当前星期 
select datePart(second, getDate());--当前秒数 
select day(getDate());--返回当前日期天数 
select day(‘2011-06-30‘);--返回当前日期天数 
select month(getDate());--返回当前日期月份 
select month(‘2011-11-10‘); 
select year(getDate());--返回当前日期年份 
select year(‘2010-11-10‘); 
select getDate();--当前系统日期 
select getUTCDate();--utc日期 
3、 数学函数 
select pi();--PI函数 
select rand(100), rand(50), rand(), rand();--随机数 
select round(rand(), 3), round(rand(100), 5);--精确小数位 
--精确位数，负数表示小数点前 
select round(123.456, 2), round(254.124, -2); 
select round(123.4567, 1, 2); 
4、 元数据 
select col_name(object_id(‘student‘), 1);--返回列名 
select col_name(object_id(‘student‘), 2); 
--该列数据类型长度 
select col_length(‘student‘, col_name(object_id(‘student‘), 2)); 
--该列数据类型长度 
select col_length(‘student‘, col_name(object_id(‘student‘), 1)); 
--返回类型名称、类型id 
select type_name(type_id(‘varchar‘)), type_id(‘varchar‘); 
--返回列类型长度 
select columnProperty(object_id(‘student‘), ‘name‘, ‘PRECISION‘); 
--返回列所在索引位置 
select columnProperty(object_id(‘student‘), ‘sex‘, ‘ColumnId‘); 
5、 字符串函数 
select ascii(‘a‘);--字符转换ascii值 
select ascii(‘A‘); 
select char(97);--ascii值转换字符 
select char(65); 
select nchar(65); 
select nchar(45231); 
select nchar(32993);--unicode转换字符 
select unicode(‘A‘), unicode(‘中‘);--返回unicode编码值 
select soundex(‘hello‘), soundex(‘world‘), soundex(‘word‘); 
select patindex(‘%a‘, ‘ta‘), patindex(‘%ac%‘, ‘jack‘), patindex(‘dex%‘, ‘dexjack‘);--匹配字符索引 
select ‘a‘ + space(2) + ‘b‘, ‘c‘ + space(5) + ‘d‘;--输出空格 
select charIndex(‘o‘, ‘hello world‘);--查找索引 
select charIndex(‘o‘, ‘hello world‘, 6);--查找索引 
select quoteName(‘abc[]def‘), quoteName(‘123]45‘); 
--精确数字 
select str(123.456, 2), str(123.456, 3), str(123.456, 4); 
select str(123.456, 9, 2), str(123.456, 9, 3), str(123.456, 6, 1), str(123.456, 9, 6); 
select difference(‘hello‘, ‘helloWorld‘);--比较字符串相同 
select difference(‘hello‘, ‘world‘); 
select difference(‘hello‘, ‘llo‘); 
select difference(‘hello‘, ‘hel‘); 
select difference(‘hello‘, ‘hello‘); 
select replace(‘abcedef‘, ‘e‘, ‘E‘);--替换字符串 
select stuff(‘hello world‘, 3, 4, ‘ABC‘);--指定位置替换字符串 
select replicate(‘abc#‘, 3);--重复字符串 
select subString(‘abc‘, 1, 1), subString(‘abc‘, 1, 2), subString(‘hello Wrold‘, 7, 5);--截取字符串 
select len(‘abc‘);--返回长度 
select reverse(‘sqlServer‘);--反转字符串 
select left(‘leftString‘, 4);--取左边字符串 
select left(‘leftString‘, 7); 
select right(‘leftString‘, 6);--取右边字符串 
select right(‘leftString‘, 3); 
select lower(‘aBc‘), lower(‘ABC‘);--小写 
select upper(‘aBc‘), upper(‘abc‘);--大写 
--去掉左边空格 
select ltrim(‘ abc‘), ltrim(‘# abc#‘), ltrim(‘ abc‘); 
--去掉右边空格 
select rtrim(‘ abc ‘), rtrim(‘# abc# ‘), rtrim(‘abc‘); 
6、 安全函数 
select current_user; 
select user; 
select user_id(), user_id(‘dbo‘), user_id(‘public‘), user_id(‘guest‘); 
select user_name(), user_name(1), user_name(0), user_name(2); 
select session_user; 
select suser_id(‘sa‘); 
select suser_sid(), suser_sid(‘sa‘), suser_sid(‘sysadmin‘), suser_sid(‘serveradmin‘); 
select is_member(‘dbo‘), is_member(‘public‘); 
select suser_name(), suser_name(1), suser_name(2), suser_name(3); 
select suser_sname(), suser_sname(0x01), suser_sname(0x02), suser_sname(0x03); 
select is_srvRoleMember(‘sysadmin‘), is_srvRoleMember(‘serveradmin‘); 
select permissions(object_id(‘student‘)); 
select system_user; 
select schema_id(), schema_id(‘dbo‘), schema_id(‘guest‘); 
select schema_name(), schema_name(1), schema_name(2), schema_name(3); 
7、 系统函数 
select app_name();--当前会话的应用程序名称 
select cast(2011 as datetime), cast(‘10‘ as money), cast(‘0‘ as varbinary);--类型转换 
select convert(datetime, ‘2011‘);--类型转换 
select coalesce(null, ‘a‘), coalesce(‘123‘, ‘a‘);--返回其参数中第一个非空表达式 
select collationProperty(‘Traditional_Spanish_CS_AS_KS_WS‘, ‘CodePage‘); 
select current_timestamp;--当前时间戳 
select current_user; 
select isDate(getDate()), isDate(‘abc‘), isNumeric(1), isNumeric(‘a‘); 
select dataLength(‘abc‘); 
select host_id(); 
select host_name(); 
select db_name(); 
select ident_current(‘student‘), ident_current(‘classes‘);--返回主键id的最大值 
select ident_incr(‘student‘), ident_incr(‘classes‘);--id的增量值 
select ident_seed(‘student‘), ident_seed(‘classes‘); 
select @@identity;--最后一次自增的值 
select identity(int, 1, 1) as id into tab from student;--将studeng表的烈属，以/1自增形式创建一个tab 
select * from tab; 
select @@rowcount;--影响行数 
select @@cursor_rows;--返回连接上打开的游标的当前限定行的数目 
select @@error;--T-SQL的错误号 
select @@procid; 
8、 配置函数 
set datefirst 7;--设置每周的第一天，表示周日 
select @@datefirst as ‘星期的第一天‘, datepart(dw, getDate()) AS ‘今天是星期‘; 
select @@dbts;--返回当前数据库唯一时间戳 
set language ‘Italian‘; 
select @@langId as ‘Language ID‘;--返回语言id 
select @@language as ‘Language Name‘;--返回当前语言名称 
select @@lock_timeout;--返回当前会话的当前锁定超时设置（毫秒） 
select @@max_connections;--返回SQL Server 实例允许同时进行的最大用户连接数 
select @@MAX_PRECISION AS ‘Max Precision‘;--返回decimal 和numeric 数据类型所用的精度级别 
select @@SERVERNAME;--SQL Server 的本地服务器的名称 
select @@SERVICENAME;--服务名 
select @@SPID;--当前会话进程id 
select @@textSize; 
select @@version;--当前数据库版本信息 
9、 系统统计函数 
select @@CONNECTIONS;--连接数 
select @@PACK_RECEIVED; 
select @@CPU_BUSY; 
select @@PACK_SENT; 
select @@TIMETICKS; 
select @@IDLE; 
select @@TOTAL_ERRORS; 
select @@IO_BUSY; 
select @@TOTAL_READ;--读取磁盘次数 
select @@PACKET_ERRORS;--发生的网络数据包错误数 
select @@TOTAL_WRITE;--sqlserver执行的磁盘写入次数 
select patIndex(‘%soft%‘, ‘microsoft SqlServer‘); 
select patIndex(‘soft%‘, ‘software SqlServer‘); 
select patIndex(‘%soft‘, ‘SqlServer microsoft‘); 
select patIndex(‘%so_gr%‘, ‘Jsonisprogram‘); 
10、 用户自定义函数 
# 查看当前数据库所有函数 
--查询所有已创建函数 
select definition,* from sys.sql_modules m join sys.objects o on m.object_id = o.object_id 
and type in(‘fn‘, ‘if‘, ‘tf‘); 
# 创建函数 
if (object_id(‘fun_add‘, ‘fn‘) is not null) 
drop function fun_add 
go 
create function fun_add(@num1 int, @num2 int) 
returns int 
with execute as caller 
as 
begin 
declare @result int; 
if (@num1 is null) 
set @num1 = 0; 
if (@num2 is null) 
set @num2 = 0; 
set @result = @num1 + @num2; 
return @result; 
end 
go 
调用函数 
select dbo.fun_add(id, age) from student; 
--自定义函数，字符串连接 
if (object_id(‘fun_append‘, ‘fn‘) is not null) 
drop function fun_append 
go 
create function fun_append(@args nvarchar(1024), @args2 nvarchar(1024)) 
returns nvarchar(2048) 
as 
begin 
return @args + @args2; 
end 
go 
select dbo.fun_append(name, ‘abc‘) from student; 
# 修改函数 
alter function fun_append(@args nvarchar(1024), @args2 nvarchar(1024)) 
returns nvarchar(1024) 
as 
begin 
declare @result varchar(1024); 
--coalesce返回第一个不为null的值 
set @args = coalesce(@args, ‘‘); 
set @args2 = coalesce(@args2, ‘‘);; 
set @result = @args + @args2; 
return @result; 
end 
go 
select dbo.fun_append(name, ‘#abc‘) from student; 
# 返回table类型函数 
--返回table对象函数 
select name, object_id, type from sys.objects where type in (‘fn‘, ‘if‘, ‘tf‘) or type like ‘%f%‘; 
if (exists (select * from sys.objects where type in (‘fn‘, ‘if‘, ‘tf‘) and name = ‘fun_find_stuRecord‘)) 
drop function fun_find_stuRecord 
go 
create function fun_find_stuRecord(@id int) 
returns table 
as 
return (select * from student where id = @id); 
go 
select * from dbo.fun_find_stuRecord(2);