高级查询在数据库中用得是最频繁的，也是应用最广泛的。
一、基本常用查询
-- SELECT
select * from student;
-- ALL 查询所有
select all sex from student;
-- DISTINCT 去重
select distinct sex from student;
-- COUNT 统计
select count(*) from student;
select count(sex) from student;
select count(distinct sex) from student;
-- TOP 顶部数据
select top 3 * from student;
-- ALIAS COLUMN NAME 列别名
select id as 编号, name as '名称', sex 性别 from student;
-- ALIAS TABLE NAME 表别名
select id, name, s.id, s.name from student s;
-- COLUMN CACULATE 列运算
select (age + id) as 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; -- id 不大于等于 3
select * from student where id !< 5; -- id 不小于等于 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 在之间
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]%'; -- 查询中间为a和o的数据
select * from student where name not like '%a%';
select * from student where name like 'ja%'; -- 查询ja开头的数据
select * from student where name not like '%[j,n]%'; -- 查询不包含j或n的数据
select * from student where name like '%[j,n,a]%' -- 查询包含字母j、n、a至少其中一个的数据
select * from student where name like '%[^ja,as,on]%' -- 查询包含字符串as或on或者不含ja字符串的数据
select * from student where name like '%[ja_on]%' -- 查询包含ja_on的数据，中间_号为任意字母
-- 查询出某列中包含mr字符的数据，其中mr可以出现在任意位置。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE '%mr%';
-- 查询出某列中包含mr字符的数据，其中mr出现在开头位置。代码如下:
SELECT * FROM 表名 WHERE 列名 LIKE 'mr%';
-- 查询出某列中包含mr字符的数据，其中mr出现在结尾位置。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE '%mr';
-- 查询出某列中前两个字符为mr、后一个字符为任意字符的数据。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE 'mr_';
-- 查询出某列中以m字符或r字符开头的数据。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE '[mr]%';
-- 查询出某列中以a~e之间的字符开头的数据，其中包括a和e。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE '[a-e]%';
-- 查询出某列中不是以m字符或r字符开头的数据。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE '[^mr]%';
-- 查询出某列中不是以a~e之间的字符开头的数据。代码如下：
SELECT * FROM 表名 WHERE 列名 LIKE '[^a-e]%';
-- 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
select count(age), age
from student
group by age;
select count(*), sex
from student
group by sex;
select count(*), sex
from student
group by sex, age
order by age;
select count(*), sex from student
where id > 2
group by sex
order by sex;
select count(*), (sex * id) as new
from student
where id > 2
group by sex * id
order by sex * id;
-- GROUP BY ALL 所有分组
select count(*), age from student group by all age;
-- HAVING 分组过滤条件
select count(*), age from student group by age having age is not null;
select count(*), cid, sex from student group by cid, sex having cid > 1;
select count(*), age from student group by age having count(age) >= 2;
select count(*), cid, sex from student group by cid, sex having cid > 1 and max(cid) > 2;
二、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者内部选择，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，统计班级学生人数
select *, (select count(*) from student where cid = classes.id) as num
from classes order by num;
# in, not in 子查询示例
# 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
);
# 查询不是班里学生的信息
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 子查询示例
# 查询存着班级id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
);
三、聚合查询
# distinct去掉重复数据
select distinct sex from student;
select count(sex), count(distinct sex) from student;
# compute和compute by汇总查询
# 对年龄大于20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20的按照新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：
- 可选
by关键字，它是每一列计算指定的行聚合。 - 行聚合函数名称，包括
sum、avg、min、count等。 - 要对齐执行聚合函数的列
compute by适合做先分组后汇合的业务。compute by后面的列一定要是order by中出现的列。
# cube汇总
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
四、排序函数
排序在很多地方需要用到，需要对查询结果今夕排序并给出序号。比如：
- 对某张表进行排序，序号需要递增不重复的。
- 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。
- 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
-- 根据排序子句给出递增的序号，但存在并列且跳空
-- 顺序递增, 每个学生按照学号递增，所以每个人都有不重复的排名
select id, name, score ,rank() over(order by cid) as rank
from student s
join score sc on sc.sid = s.id;
-- 跳过相同递增, 比如有一个人考100分则为第一名，10个人考99分则都是第二名，考98的就是12名了
select s.id, s.name, cid, c.name, score, rank() over(order by score) as 排名
from student s
join score sc on sc.sid = s.id;
# dense_rank函数
-- 不跳过相同递增, 比如有一个人考100分则为第一名，10个人考99分则都是第二名，考98的就是三名
select s.id, s.name, cid, c.name, score, dense_rank() over(order by score) as 排名
from student s
join score sc on sc.sid = s.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
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;
五、集合运算
操作两组查询结果，进行交集、并集、减集运算
# union 和 union all 进行并集运算
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;
# intersect 进行交集运算
-- 交集(相同部分)
select * from student where name like 'ja%'
intersect
select * from student;
# 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%';
六、公式表表达式
查询的时候，有时候中间表需要重复使用，这些子查询被重复查询调用，补单效率低，而且可读性低，不利于理解。那么公示表表达式可以解决这个问题。
我们可以将公示表表达式(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;
七、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;
-- left join 左连接
select s.id, s.name, c.id, c.name from student s left join classes c on s.cid = c.id;
-- right join 右连接
select s.id, s.name, c.id, c.name from student s right join classes c on s.cid = c.id;
-- inner join 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;
-- cross join 交叉连接，结果是一个笛卡尔乘积
select s.id, s.name, c.id, c.name from student s cross join classes c where s.cid = c.id;
-- 自连接(同一张表进行连接查询)
select distinct s.* from student s, student s1 where s.id <> s1.id and s.sex = s1.sex;
八、函数
# 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;
# 日期时间函数
select dateAdd(day, 3, getDate()); -- 加3天
select dateAdd(year, 3, getDate()); -- 加3年
select dateAdd(hour, 3, getDate()); -- 加3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, '2020-05-24', getDate());
-- 相差秒数
select dateDiff(second, '2020-05-24 12:00:00', getDate());
-- 相差小时数
select dateDiff(hour, '2020-05-24 12:00:00', getDate());
select dateName(month, getDate());
select dateName(minute, getDate());
select dateName(weekday, getDate());
select datePart(month, getDate());
select datePart(weekday, getDate());
select datePart(second, getDate());
select day(getDate());
select day('2020-05-24');
select month(getDate());
select month('2020-05-24');
select year(getDate());
select year('2020-05-24');
select getDate();
select getUTCDate();
# 数学函数
select pi();
select rand(100), rand(50), rand(), rand();
select round(rand(), 3), round(rand(100), 5);
-- 精确位数，负数表示小数点前
select round(123.456, 2), round(254.123, -2);
select round(123.4567, 1, 2);
# 元数据
select col_name(object_id('student'), 1);
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));
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');
# 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');
# 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);
# 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;
# 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
# 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');
九、自定义函数
# 查看当前数据库的所有函数
-- 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) return 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)) return 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)) return nvarchar(1024)
as
begin
declare @result varchar(1024);
-- coalesce 返回第一个不为null的值
set @args = coalesce(@args, '');
set @args = coalesce(@args2, '');
set @result = @args + @args2;
return @result;
end
go
select dbp.fun_append(name, '#abc') from student;
# 返回table类型函数
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)
return table
as
return (select * from student where id = @id);
go
select * from dbo.fun_find_stuRecord(2);
