Ø 基本常用查詢
--select
select * from student;
--all 查詢所有
select all sex from student;
--distinct 過(guò)濾重復(fù)
select distinct sex from student;
--count 統(tǒng)計(jì)
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(hào), 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(yùn)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 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 ... 相當(dāng)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(jìn)行分組統(tǒng)計(jì)
select count(age), age from student group by age;
按照性別進(jìn)行分組統(tǒng)計(jì)
select count(*), sex from student group by sex;
按照年齡和性別組合分組統(tǒng)計(jì)，并排序
select count(*), sex from student group by sex, age order by age;
按照性別分組，并且是id大于2的記錄最后按照性別排序
select count(*), sex from student where id > 2 group by sex order by sex;
查詢id大于2的數(shù)據(jù)，并完成運(yùn)算后的結(jié)果進(jìn)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(guò)濾條件
按照年齡分組，過(guò)濾年齡為空的數(shù)據(jù)，并且統(tǒng)計(jì)分組的條數(shù)和現(xiàn)實(shí)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(guò)濾條件是cid大于1的記錄
select count(*), cid, sex from student group by cid, sex having cid > 1;
按照年齡分組，過(guò)濾條件是分組后的記錄條數(shù)大于等于2
select count(*), age from student group by age having count(age) >= 2;
按照cid和性別組合分組，過(guò)濾條件是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;
Ø 嵌套子查詢
子查詢是一個(gè)嵌套在select、insert、update或delete語(yǔ)句或其他子查詢中的查詢。任何允許使用表達(dá)式的地方都可以使用子查詢。子查詢也稱為內(nèi)部查詢或內(nèi)部選擇，而包含子查詢的語(yǔ)句也成為外部查詢或外部選擇。
# from (select … table)示例
將一個(gè)table的查詢結(jié)果當(dāng)做一個(gè)新表進(jìn)行查詢
select * from (
select id, name from student where sex = 1
) t where t.id > 2;
上面括號(hào)中的語(yǔ)句，就是子查詢語(yǔ)句（內(nèi)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(yǔ)句：
1、 包含常規(guī)選擇列表組件的常規(guī)select查詢
2、 包含一個(gè)或多個(gè)表或視圖名稱的常規(guī)from語(yǔ)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(jí)信息，統(tǒng)計(jì)班級(jí)學(xué)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(jí)id大于小于的這些班級(jí)的學(xué)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(xué)生信息
select * from student where cid not in (
select id from classes where name = '2班'
)
in、not in 后面的子句返回的結(jié)果必須是一列，這一列的結(jié)果將會(huì)作為查詢條件對(duì)應(yīng)前面的條件。如cid對(duì)應(yīng)子句的id；
# exists和not exists子句查詢示例
查詢存在班級(jí)id為的學(xué)生信息
select * from student where exists (
select * from classes where id = student.cid and id = 3
);
查詢沒(méi)有分配班級(jí)的學(xué)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(nèi)部查詢和外部查詢進(jìn)行一個(gè)關(guān)聯(lián)的條件，如果沒(méi)有這個(gè)條件將是查詢到的所有信息。如：id等于student.id；
# some、any、all子句查詢示例
查詢班級(jí)的學(xué)生年齡大于班級(jí)的學(xué)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(fù)數(shù)據(jù)
select distinct sex from student;
select count(sex), count(distinct sex) from student;
2、 compute和compute by匯總查詢
對(duì)年齡大于的進(jìn)行匯總
select age from student
where age > 20 order by age compute sum(age) by age;
對(duì)年齡大于的按照性別進(jìn)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(jìn)行匯總前面是查詢的結(jié)果，后面一條結(jié)果集就是匯總的信息。compute子句中可以添加多個(gè)匯總表達(dá)式，可以添加的信息如下：
a、 可選by關(guān)鍵字。它是每一列計(jì)算指定的行聚合
b、 行聚合函數(shù)名稱。包括sum、avg、min、max、count等
c、 要對(duì)其執(zhí)行聚合函數(shù)的列
compute by適合做先分組后匯總的業(yè)務(wù)。compute by后面的列一定要是order by中出現(xiàn)的列。
3、 cube匯總
cube匯總和compute效果類(lèi)似，但語(yǔ)法較簡(jiǎn)潔，而且返回的是一個(gè)結(jié)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(jié)合group by語(yǔ)句完成分組匯總
Ø 排序函數(shù)
排序在很多地方需要用到，需要對(duì)查詢結(jié)果進(jìn)行排序并且給出序號(hào)。比如：
1、 對(duì)某張表進(jìn)行排序，序號(hào)需要遞增不重復(fù)的
2、 對(duì)學(xué)生的成績(jī)進(jìn)行排序，得出名次，名次可以并列，但名次的序號(hào)是連續(xù)遞增的
3、 在某些排序的情況下，需要跳空序號(hào)，雖然是并列
基本語(yǔ)法
排序函數(shù) over([分組語(yǔ)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(shù)
根據(jù)排序子句給出遞增連續(xù)序號(hào)
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(shù)函數(shù)
根據(jù)排序子句給出遞增的序號(hào)，但是存在并列并且跳空
順序遞增
select id, name, rank() over(order by cid) as rank from student;
跳過(guò)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(shù)
根據(jù)排序子句給出遞增的序號(hào)，但是存在并列不跳空
不跳過(guò)，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(duì)分組的數(shù)據(jù)進(jìn)行增加排序，partition by可以與以上三個(gè)函數(shù)聯(lián)合使用。
利用partition by按照班級(jí)名稱分組，學(xué)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(shù)
將要排序的數(shù)據(jù)進(jìn)行平分，然后按照等分排序。ntile中的參數(shù)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(yùn)算
操作兩組查詢結(jié)果，進(jìn)行交集、并集、減集運(yùn)算
1、 union和union all進(jìn)行并集運(yùn)算
--union 并集、不重復(fù)
select id, name from student where name like 'ja%'
union
select id, name from student where id = 4;
--并集、重復(fù)
select * from student where name like 'ja%'
union all
select * from student;
2、 intersect進(jìn)行交集運(yùn)算
--交集（相同部分）
select * from student where name like 'ja%'
intersect
select * from student;
3、 except進(jìn)行減集運(yùn)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(dá)式
查詢表的時(shí)候，有時(shí)候中間表需要重復(fù)使用，這些子查詢被重復(fù)查詢調(diào)用，不但效率低，而且可讀性低，不利于理解。那么公式表表達(dá)式可以解決這個(gè)問(wèn)題。
我們可以將公式表表達(dá)式（CET）視為臨時(shí)結(jié)果集，在select、insert、update、delete或是create view語(yǔ)句的執(zhí)行范圍內(nèi)進(jìn)行定義。
--表達(dá)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(jiǎn)化連接查詢
--簡(jiǎn)化聯(lián)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(nèi)連接
--內(nèi)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(lián)接查詢，結(jié)果是一個(gè)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(jìn)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(shù)
1、 聚合函數(shù)
max最大值、min最小值、count統(tǒng)計(jì)、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(shí)間函數(shù)
select dateAdd(day, 3, getDate());--加天
select dateAdd(year, 3, getDate());--加年
select dateAdd(hour, 3, getDate());--加小時(shí)
--返回跨兩個(gè)指定日期的日期邊界數(shù)和時(shí)間邊界數(shù)
select dateDiff(day, '2011-06-20', getDate());
--相差秒數(shù)
select dateDiff(second, '2011-06-22 11:00:00', getDate());
--相差小時(shí)數(shù)
select dateDiff(hour, '2011-06-22 10:00:00', getDate());
select dateName(month, getDate());--當(dāng)前月份
select dateName(minute, getDate());--當(dāng)前分鐘
select dateName(weekday, getDate());--當(dāng)前星期
select datePart(month, getDate());--當(dāng)前月份
select datePart(weekday, getDate());--當(dāng)前星期
select datePart(second, getDate());--當(dāng)前秒數(shù)
select day(getDate());--返回當(dāng)前日期天數(shù)
select day('2011-06-30');--返回當(dāng)前日期天數(shù)
select month(getDate());--返回當(dāng)前日期月份
select month('2011-11-10');
select year(getDate());--返回當(dāng)前日期年份
select year('2010-11-10');
select getDate();--當(dāng)前系統(tǒng)日期
select getUTCDate();--utc日期
3、 數(shù)學(xué)函數(shù)
select pi();--PI函數(shù)
select rand(100), rand(50), rand(), rand();--隨機(jī)數(shù)
select round(rand(), 3), round(rand(100), 5);--精確小數(shù)位
--精確位數(shù)，負(fù)數(shù)表示小數(shù)點(diǎn)前
select round(123.456, 2), round(254.124, -2);
select round(123.4567, 1, 2);
4、 元數(shù)據(jù)
select col_name(object_id('student'), 1);--返回列名
select col_name(object_id('student'), 2);
--該列數(shù)據(jù)類(lèi)型長(zhǎng)度
select col_length('student', col_name(object_id('student'), 2));
--該列數(shù)據(jù)類(lèi)型長(zhǎng)度
select col_length('student', col_name(object_id('student'), 1));
--返回類(lèi)型名稱、類(lèi)型id
select type_name(type_id('varchar')), type_id('varchar');
--返回列類(lèi)型長(zhǎng)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(shù)
select ascii('a');--字符轉(zhuǎn)換ascii值
select ascii('A');
select char(97);--ascii值轉(zhuǎn)換字符
select char(65);
select nchar(65);
select nchar(45231);
select nchar(32993);--unicode轉(zhuǎn)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(shù)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(fù)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(zhǎng)度
select reverse('sqlServer');--反轉(zhuǎn)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(xiě)
select upper('aBc'), upper('abc');--大寫(xiě)
--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(shù)
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(tǒng)函數(shù)
select app_name();--當(dāng)前會(huì)話的應(yīng)用程序名稱
select cast(2011 as datetime), cast('10' as money), cast('0' as varbinary);--類(lèi)型轉(zhuǎn)換
select convert(datetime, '2011');--類(lèi)型轉(zhuǎn)換
select coalesce(null, 'a'), coalesce('123', 'a');--返回其參數(shù)中第一個(gè)非空表達(dá)式
select collationProperty('Traditional_Spanish_CS_AS_KS_WS', 'CodePage');
select current_timestamp;--當(dāng)前時(shí)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;--最后一次自增的值
select identity(int, 1, 1) as id into tab from student;--將studeng表的烈屬，以/1自增形式創(chuàng)建一個(gè)tab
select * from tab;
select @@rowcount;--影響行數(shù)
select @@cursor_rows;--返回連接上打開(kāi)的游標(biāo)的當(dāng)前限定行的數(shù)目
select @@error;--T-SQL的錯(cuò)誤號(hào)
select @@procid;
8、 配置函數(shù)
set datefirst 7;--設(shè)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(dāng)前數(shù)據(jù)庫(kù)唯一時(shí)間戳
set language 'Italian';
select @@langId as 'Language ID';--返回語(yǔ)言id
select @@language as 'Language Name';--返回當(dāng)前語(yǔ)言名稱
select @@lock_timeout;--返回當(dāng)前會(huì)話的當(dāng)前鎖定超時(shí)設(shè)置（毫秒）
select @@max_connections;--返回SQL Server 實(shí)例允許同時(shí)進(jìn)行的最大用戶連接數(shù)
select @@MAX_PRECISION AS 'Max Precision';--返回decimal 和numeric 數(shù)據(jù)類(lèi)型所用的精度級(jí)別
select @@SERVERNAME;--SQL Server 的本地服務(wù)器的名稱
select @@SERVICENAME;--服務(wù)名
select @@SPID;--當(dāng)前會(huì)話進(jìn)程id
select @@textSize;
select @@version;--當(dāng)前數(shù)據(jù)庫(kù)版本信息
9、 系統(tǒng)統(tǒng)計(jì)函數(shù)
select @@CONNECTIONS;--連接數(shù)
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(pán)次數(shù)
select @@PACKET_ERRORS;--發(fā)生的網(wǎng)絡(luò)數(shù)據(jù)包錯(cuò)誤數(shù)
select @@TOTAL_WRITE;--sqlserver執(zhí)行的磁盤(pán)寫(xiě)入次數(shù)
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(shù)
# 查看當(dāng)前數(shù)據(jù)庫(kù)所有函數(shù)
--查詢所有已創(chuàng)建函數(shù)
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(chuàng)建函數(shù)
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(diào)用函數(shù)
select dbo.fun_add(id, age) from student;
--自定義函數(shù)，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(shù)
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(gè)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(lèi)型函數(shù)
--返回table對(duì)象函數(shù)
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);