【SQL】高级函数汇总
基本常用查询
-- all 查询所有,几乎从来不用 all 关键字,因为是默认关键字 select all sex from student; -- distinct 过滤重复 (常用语检查一列数据是否有异常值) select distinct sex from student; -- count 统计 select count(distinct sex) from student; -- top 取前N条记录 select top 3 * from student; -- 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; -- 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。
-- 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
-- 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; -- 查询班级id大于小于X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X班的学生信息 select * from student where cid not in ( select id from classes where name = '2班' ) -- all,any,some 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; -- 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 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。 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
-- union 并集、不重复 select id, name from student where name like 'ja%' union select id, name from student where id = 4; -- union all 并集、重复 select * from student where name like 'ja%' union all select * from student; -- 交集（相同部分） select * from student where name like 'ja%' intersect select * from student; -- 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。
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;
表的联合查询
-- 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; -- 左连接 (左为基表) select s.id, s.name, c.id, c.name from student s left join classes c on s.cid = c.id; -- 右连接 (右为基表) select s.id, s.name, c.id, c.name from student s right join classes c on s.cid = c.id; -- 内连接 (等值联合) select s.id, s.name, c.id, c.name from student s inner join classes c on s.cid = c.id; -- 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 ,classes c -- 自连接 select distinct s.* from student s, student s1 where s.id <> s1.id and s.sex = s1.sex;
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()); select dateAdd(year, 3, getDate()); select dateAdd(hour, 3, getDate()); select dateDiff(day, '2011-06-20', getDate()); select dateDiff(second, '2011-06-22 11:00:00', getDate()); select dateDiff(hour, '2011-06-22 10:00:00', 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('2011-06-30'); select month(getDate()); select month('2011-11-10'); select year(getDate()); select year('2010-11-10'); select getDate(); select getUTCDate(); -- 数学函数 select pi(); select rand(100), rand(50), rand(); select round(rand(), 3), round(rand(100), 5); select round(123.456, 2), round(254.124, -2); select round(123.4567, 1, 2); -- 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'); -- 字符串函数 select ascii('a'); select ascii('A'); select char(97); select char(65); select nchar(65); select nchar(45231); select nchar(32993); select unicode('A'), unicode('中'); select soundex('hello'), soundex('world'), soundex('word'); select patindex('%a', 'ta'), patindex('%ac%', 'jack'), patindex('dex%', 'dexjack'); select 'a' + space(2) + 'b', 'c' + space(5) + 'd'; select charIndex('o', 'hello world'); select charIndex('o', 'hello world', 6); select quoteName('abc[]def'), quoteName('123]45'); 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'); select difference('hello', 'world'); select difference('hello', 'llo'); select difference('hello', 'hel'); select difference('hello', 'hello'); select replace('abcedef', 'e', 'E'); select stuff('hello world', 3, 4, 'ABC'); select replicate('abc#', 3); select subString('abc', 1, 1), subString('abc', 1, 2), subString('hello Wrold', 7, 5); select len('abc'); select reverse('sqlServer'); select left('leftString', 4); select left('leftString', 7); select right('leftString', 6); select right('leftString', 3); select lower('aBc'), lower('ABC'); select upper('aBc'), upper('abc'); select ltrim(' abc'), ltrim('# abc#'), ltrim(' abc'); 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 @@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; select @@PACK_RECEIVED; select @@CPU_BUSY; select @@PACK_SENT; select @@TIMETICKS; select @@IDLE; select @@TOTAL_ERRORS; select @@IO_BUSY; select @@TOTAL_READ; select @@PACKET_ERRORS; select @@TOTAL_WRITE; select patIndex('%soft%', 'microsoft SqlServer'); select patIndex('soft%', 'software SqlServer'); select patIndex('%soft', 'SqlServer microsoft'); select patIndex('%so_gr%', 'Jsonisprogram'); -- 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);
转自大神：https://blog.csdn.net/wang1127248268/article/details/53406564
