Ø 基本常用查詢
--select
select * from student;
--all 查詢所有
select all sex from student;
--distinct 過濾重復
select distinct sex from student;
--count 統計
select count(*) from student;
select count(sex) from student;
select count(distinct sex) from student;
--top 取前N條記錄
select top 3 * from student;
--alias column name 列重命名
select id as 編號, name '名稱', sex 性別 from student;
--alias table name 表重命名
select id, name, s.id, s.name from student s;
--column 列運算
select (age + id) col from student;
select s.name + '-' + c.name from classes c, student s where s.cid = c.id;
--where 條件
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 並且
select * from student where id > 2 and sex = 1;
--or 或者
select * from student where id = 2 or sex = 1;
--between ... and ... 相當於並且
select * from student where id between 2 and 5;
select * from student where id not between 2 and 5;
--like 模糊查詢
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 子查詢
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 不為空
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 分組
按照年齡進行分組統計
select count(age), age from student group by age;
按照性別進行分組統計
select count(*), sex from student group by sex;
按照年齡和性別組合分組統計，並排序
select count(*), sex from student group by sex, age order by age;
按照性別分組，並且是id大於2的記錄最後按照性別排序
select count(*), sex from student where id > 2 group by sex order by sex;
查詢id大於2的數據，並完成運算後的結果進行分組和排序
select count(*), (sex * id) new from student where id > 2 group by sex * id order by sex * id;
--group by all 所有分組
按照年齡分組，是所有的年齡
select count(*), age from student group by all age;
--having 分組過濾條件
按照年齡分組，過濾年齡為空的數據，並且統計分組的條數和現實年齡信息
select count(*), age from student group by age having age is not null;
按照年齡和cid組合分組，過濾條件是cid大於1的記錄
select count(*), cid, sex from student group by cid, sex having cid > 1;
按照年齡分組，過濾條件是分組後的記錄條數大於等於2
select count(*), age from student group by age having count(age) >= 2;
按照cid和性別組合分組，過濾條件是cid大於1，cid的最大值大於2
select count(*), cid, sex from student group by cid, sex having cid > 1 and max(cid) > 2;
Ø 嵌套子查詢
子查詢是一個嵌套在select、insert、update或delete語句或其他子查詢中的查詢。任何允許使用表達式的地方都可以使用子查詢。子查詢也稱為內部查詢或內部選擇，而包含子查詢的語句也成為外部查詢或外部選擇。
# from (select … table)示例
將一個table的查詢結果當做一個新表進行查詢
select * from (
select id, name from student where sex = 1
) t where t.id > 2;
上面括號中的語句，就是子查詢語句（內部查詢）。在外面的是外部查詢，其中外部查詢可以包含以下語句：
1、 包含常規選擇列表組件的常規select查詢
2、 包含一個或多個表或視圖名稱的常規from語句
3、 可選的where子句
4、 可選的group by子句
5、 可選的having子句
# 示例
查詢班級信息，統計班級學生人生
select *, (select count(*) from student where cid = classes.id) as num
from classes order by num;
# in, not in子句查詢示例
查詢班級id大於小於的這些班級的學生信息
select * from student where cid in (
select id from classes where id > 2 and id < 4
);
查詢不是班的學生信息
select * from student where cid not in (
select id from classes where name = '2班'
)
in、not in 後面的子句返回的結果必須是一列，這一列的結果將會作為查詢條件對應前面的條件。如cid對應子句的id；
# exists和not exists子句查詢示例
查詢存在班級id為的學生信息
select * from student where exists (
select * from classes where id = student.cid and id = 3
);
查詢沒有分配班級的學生信息
select * from student where not exists (
select * from classes where id = student.cid
);
exists和not exists查詢需要內部查詢和外部查詢進行一個關聯的條件，如果沒有這個條件將是查詢到的所有信息。如：id等於student.id；
# some、any、all子句查詢示例
查詢班級的學生年齡大於班級的學生的年齡的信息
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
);
Ø 聚合查詢
1、 distinct去掉重復數據
select distinct sex from student;
select count(sex), count(distinct sex) from student;
2、 compute和compute by匯總查詢
對年齡大於的進行匯總
select age from student
where age > 20 order by age compute sum(age) by age;
對年齡大於的按照性別進行分組匯總年齡信息
select id, sex, age from student
where age > 20 order by sex, age compute sum(age) by sex;
按照年齡分組匯總
select age from student
where age > 20 order by age, id compute sum(age);
按照年齡分組，年齡匯總，id找最大值
select id, age from student
where age > 20 order by age compute sum(age), max(id);
compute進行匯總前面是查詢的結果，後面一條結果集就是匯總的信息。compute子句中可以添加多個匯總表達式，可以添加的信息如下：
a、 可選by關鍵字。它是每一列計算指定的行聚合
b、 行聚合函數名稱。包括sum、avg、min、max、count等
c、 要對其執行聚合函數的列
compute by適合做先分組後匯總的業務。compute by後面的列一定要是order by中出現的列。
3、 cube匯總
cube匯總和compute效果類似，但語法較簡潔，而且返回的是一個結果集。
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要結合group by語句完成分組匯總
Ø 排序函數
排序在很多地方需要用到，需要對查詢結果進行排序並且給出序號。比如：
1、 對某張表進行排序，序號需要遞增不重復的
2、 對學生的成績進行排序，得出名次，名次可以並列，但名次的序號是連續遞增的
3、 在某些排序的情況下，需要跳空序號，雖然是並列
基本語法
排序函數 over([分組語句] 排序子句[desc][asc])
排序子句 order by 列名, 列名
分組子句 partition by 分組列, 分組列
# row_number函數
根據排序子句給出遞增連續序號
按照名稱排序的順序遞增
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函數函數
根據排序子句給出遞增的序號，但是存在並列並且跳空
順序遞增
select id, name, rank() over(order by cid) as rank from student;
跳過相同遞增
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函數
根據排序子句給出遞增的序號，但是存在並列不跳空
不跳過，直接遞增
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分組子句
可以完成對分組的數據進行增加排序，partition by可以與以上三個函數聯合使用。
利用partition by按照班級名稱分組，學生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平均排序函數
將要排序的數據進行平分，然後按照等分排序。ntile中的參數代表分成多少等分。
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;
Ø 集合運算
操作兩組查詢結果，進行交集、並集、減集運算
1、 union和union all進行並集運算
--union 並集、不重復
select id, name from student where name like 'ja%'
union
select id, name from student where id = 4;
--並集、重復
select * from student where name like 'ja%'
union all
select * from student;
2、 intersect進行交集運算
--交集（相同部分）
select * from student where name like 'ja%'
intersect
select * from student;
3、 except進行減集運算
--減集（除相同部分）
select * from student where name like 'ja%'
except
select * from student where name like 'jas%';
Ø 公式表表達式
查詢表的時候，有時候中間表需要重復使用，這些子查詢被重復查詢調用，不但效率低，而且可讀性低，不利於理解。那麼公式表表達式可以解決這個問題。
我們可以將公式表表達式（CET）視為臨時結果集，在select、insert、update、delete或是create view語句的執行范圍內進行定義。
--表達式
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;
Ø 連接查詢
1、 簡化連接查詢
--簡化聯接查詢
select s.id, s.name, c.id, c.name from student s, classes c where s.cid = c.id;
2、 left join左連接
--左連接
select s.id, s.name, c.id, c.name from student s left join classes c on s.cid = c.id;
3、 right join右連接
--右連接
select s.id, s.name, c.id, c.name from student s right join classes c on s.cid = c.id;
4、 inner join內連接
--內連接
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交叉連接
--交叉聯接查詢，結果是一個笛卡兒乘積
select s.id, s.name, c.id, c.name from student s cross join classes c
--where s.cid = c.id;
6、 自連接（同一張表進行連接查詢）
--自連接
select distinct s.* from student s, student s1 where s.id <> s1.id and s.sex = s1.sex;
Ø 函數
1、 聚合函數
max最大值、min最小值、count統計、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、 日期時間函數
select dateAdd(day, 3, getDate());--加天
select dateAdd(year, 3, getDate());--加年
select dateAdd(hour, 3, getDate());--加小時
--返回跨兩個指定日期的日期邊界數和時間邊界數
select dateDiff(day, '2011-06-20', getDate());
--相差秒數
select dateDiff(second, '2011-06-22 11:00:00', getDate());
--相差小時數
select dateDiff(hour, '2011-06-22 10:00:00', getDate());
select dateName(month, getDate());--當前月份
select dateName(minute, getDate());--當前分鐘
select dateName(weekday, getDate());--當前星期
select datePart(month, getDate());--當前月份
select datePart(weekday, getDate());--當前星期
select datePart(second, getDate());--當前秒數
select day(getDate());--返回當前日期天數
select day('2011-06-30');--返回當前日期天數
select month(getDate());--返回當前日期月份
select month('2011-11-10');
select year(getDate());--返回當前日期年份
select year('2010-11-10');
select getDate();--當前系統日期
select getUTCDate();--utc日期
3、 數學函數
select pi();--PI函數
select rand(100), rand(50), rand(), rand();--隨機數
select round(rand(), 3), round(rand(100), 5);--精確小數位
--精確位數，負數表示小數點前
select round(123.456, 2), round(254.124, -2);
select round(123.4567, 1, 2);
4、 元數據
select col_name(object_id('student'), 1);--返回列名
select col_name(object_id('student'), 2);
--該列數據類型長度
select col_length('student', col_name(object_id('student'), 2));
--該列數據類型長度
select col_length('student', col_name(object_id('student'), 1));
--返回類型名稱、類型id
select type_name(type_id('varchar')), type_id('varchar');
--返回列類型長度
select columnProperty(object_id('student'), 'name', 'PRECISION');
--返回列所在索引位置
select columnProperty(object_id('student'), 'sex', 'ColumnId');
5、 字符串函數
select ascii('a');--字符轉換ascii值
select ascii('A');
select char(97);--ascii值轉換字符
select char(65);
select nchar(65);
select nchar(45231);
select nchar(32993);--unicode轉換字符
select unicode('A'), unicode('中');--返回unicode編碼值
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';--輸出空格
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');
--精確數字
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');--比較字符串相同
select difference('hello', 'world');
select difference('hello', 'llo');
select difference('hello', 'hel');
select difference('hello', 'hello');
select replace('abcedef', 'e', 'E');--替換字符串
select stuff('hello world', 3, 4, 'ABC');--指定位置替換字符串
select replicate('abc#', 3);--重復字符串
select subString('abc', 1, 1), subString('abc', 1, 2), subString('hello Wrold', 7, 5);--截取字符串
select len('abc');--返回長度
select reverse('sqlServer');--反轉字符串
select left('leftString', 4);--取左邊字符串
select left('leftString', 7);
select right('leftString', 6);--取右邊字符串
select right('leftString', 3);
select lower('aBc'), lower('ABC');--小寫
select upper('aBc'), upper('abc');--大寫
--去掉左邊空格
select ltrim(' abc'), ltrim('# abc#'), ltrim(' abc');
--去掉右邊空格
select rtrim(' abc '), rtrim('# abc# '), rtrim('abc');
6、 安全函數
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、 系統函數
select app_name();--當前會話的應用程序名稱
select cast(2011 as datetime), cast('10' as money), cast('0' as varbinary);--類型轉換
select convert(datetime, '2011');--類型轉換
select coalesce(null, 'a'), coalesce('123', 'a');--返回其參數中第一個非空表達式
select collationProperty('Traditional_Spanish_CS_AS_KS_WS', 'CodePage');
select current_timestamp;--當前時間戳
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');--返回主鍵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;--最後一次自增的值
select identity(int, 1, 1) as id into tab from student;--將studeng表的烈屬，以/1自增形式創建一個tab
select * from tab;
select @@rowcount;--影響行數
select @@cursor_rows;--返回連接上打開的游標的當前限定行的數目
select @@error;--T-SQL的錯誤號
select @@procid;
8、 配置函數
set datefirst 7;--設置每周的第一天，表示周日
select @@datefirst as '星期的第一天', datepart(dw, getDate()) AS '今天是星期';
select @@dbts;--返回當前數據庫唯一時間戳
set language 'Italian';
select @@langId as 'Language ID';--返回語言id
select @@language as 'Language Name';--返回當前語言名稱
select @@lock_timeout;--返回當前會話的當前鎖定超時設置（毫秒）
select @@max_connections;--返回SQL Server 實例允許同時進行的最大用戶連接數
select @@MAX_PRECISION AS 'Max Precision';--返回decimal 和numeric 數據類型所用的精度級別
select @@SERVERNAME;--SQL Server 的本地服務器的名稱
select @@SERVICENAME;--服務名
select @@SPID;--當前會話進程id
select @@textSize;
select @@version;--當前數據庫版本信息
9、 系統統計函數
select @@CONNECTIONS;--連接數
select @@PACK_RECEIVED;
select @@CPU_BUSY;
select @@PACK_SENT;
select @@TIMETICKS;
select @@IDLE;
select @@TOTAL_ERRORS;
select @@IO_BUSY;
select @@TOTAL_READ;--讀取磁盤次數
select @@PACKET_ERRORS;--發生的網絡數據包錯誤數
select @@TOTAL_WRITE;--sqlserver執行的磁盤寫入次數
select patIndex('%soft%', 'microsoft SqlServer');
select patIndex('soft%', 'software SqlServer');
select patIndex('%soft', 'SqlServer microsoft');
select patIndex('%so_gr%', 'Jsonisprogram');
10、 用戶自定義函數
# 查看當前數據庫所有函數
--查詢所有已創建函數
select definition,* from sys.sql_modules m join sys.objects o on m.object_id = o.object_id
and type in('fn', 'if', 'tf');
# 創建函數
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
調用函數
select dbo.fun_add(id, age) from student;
--自定義函數，字符串連接
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;
# 修改函數
alter function fun_append(@args nvarchar(1024), @args2 nvarchar(1024))
returns nvarchar(1024)
as
begin
declare @result varchar(1024);
--coalesce返回第一個不為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類型函數
--返回table對象函數
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);
