高級查詢在數據庫中用得是最頻繁的，也是應用最廣泛的。

? 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 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，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的數據，并完成運算后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，并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，過濾條件是分組后的記錄條數大于等于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;

? 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。

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# 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

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# 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;

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# in, not in子句查詢示例

查詢班級id大于小于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 后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；

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# 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notexists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等于student.id；

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# some、any、all子句查詢示例

查詢班級的學生年齡大于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 );

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? 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;

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2、 compute和compute by匯總查詢

對年齡大于的進行匯總 select age from student where age > 20 order by age compute sum(age) by age; ? 對年齡大于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，后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適合做先分組后匯總的業務。compute by后面的列一定要是order by中出現的列。

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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

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? 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并且給出序號。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，名次可以并列，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，雖然是并列

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

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# 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;

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# rank函數函數

根據排序子句給出遞增的序號，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;

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# dense_rank函數

根據排序子句給出遞增的序號，但是存在并列不跳空

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;

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# 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;

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# ntile平均排序函數

將要排序的數據進行平分，然后按照等分排序。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;

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? 集合運算

操作兩組查詢結果，進行交集、并集、減集運算

1、 union和union all進行并集運算

--union 并集、不重復 select id, name from student where name like 'ja%' union select id, name from student where id = 4; ? --并集、重復 select * from student where name like 'ja%' union all select * from student;

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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;

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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%';

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? 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，不利于理解。那么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createview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;

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? 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;

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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;

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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;

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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;

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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;

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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

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