各種SQL查詢技巧彙總 (轉)

阿新 • • 發佈：2019-01-09

select
select * from student;

all 查詢所有
select all sex from student;

distinct 過濾重複
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 列重新命名
select id as 編號, name ‘名稱’, sex 性別 from student;

alias table name 表重新命名
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的資料，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，過濾年齡為空的資料，並且統計分組的條數和現實年齡資訊
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;
巢狀子查詢

子查詢是一個巢狀在select、insert、update或delete語句或其他子查詢中的查詢。任何允許使用表示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、包含常規選擇列表元件的常規select查詢
2、包含一個或多個表或檢視名稱的常規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

查詢班級資訊，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資訊
select * from student where cid in (
select id from classes where id > 2 and id < 4
);

查詢不是班的學生資訊
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為的學生資訊
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資訊
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資訊。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資訊
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
);
聚合查詢

1、 distinct去掉重複資料
select distinct sex from student;
select count(sex), count(distinct sex) from student;

2、 compute和compute by彙總查詢
對年齡大於的進行彙總
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彙總年齡資訊
select id, sex, age from student
where age > 20 order by sex, age compute sum(age) by sex;

按照年齡分組彙總
select age from student
where age > 20 order by age, id compute sum(age);

按照年齡分組，年齡彙總，id找最大值
select id, age from student
where age > 20 order by age compute sum(age), max(id);
compute進行彙總前面是查詢的結果，後面一條結果集就是彙總的資訊。compute子句中可以新增多個彙總表示式，可以新增的資訊如下：
a、可選by關鍵字。它是每一列計算指定的行聚合
b、行聚合函式名稱。包括sum、avg、min、max、count等
c、要對其執行聚合函式的列
compute by適合做先分組後彙總的業務。compute by後面的列一定要是order by中出現的列。

3、 cube彙總
cube彙總和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語句完成分組彙總
排序函式

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，序號需要遞增不重複的
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
排序函式 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函式

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函式函式

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函式

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

可以完成對分組的資料進行增加排序，partition by可以與以上三個函式聯合使用。
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平均排序函式

將要排序的資料進行平分，然後按照等分排序。ntile中的引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;
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、不重複
select id, name from student where name like ‘ja%’
union
select id, name from student where id = 4;

–並集、重複
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%’;
公式表表達式

查詢表的時候，有時候中間表需要重複使用，這些子查詢被重複查詢呼叫，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語句的執行範圍內進行定義。
– 表示式
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;
連線查詢

1、簡化連線查詢

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左連線

左連線
select s.id, s.name, c.id, c.name from student s left join classes c on s.cid = c.id;

3、 right join右連線

右連線
select s.id, s.name, c.id, c.name from student s right join classes c on s.cid = c.id;

4、 inner join內連線

內連線
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;

1、聚合函式
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、日期時間函式
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

各種SQL查詢技巧彙總 (轉)

各種SQL查詢技巧彙總 (轉)

SQL查詢語句中行轉列的顯示

Oracle 動態SQL實現SQL查詢子集行轉列

SQL查詢語句行轉列橫向顯示

JDBC操作各種資料庫經驗技巧集萃(轉）

sql查詢結果行轉列, 有多少行就轉多少列

Databricks 第11篇：Spark SQL 查詢（行轉列、列轉行、Lateral View、排序）

SQL查詢一個表中另外一個表不存在的數據-轉

SQL查詢今天、昨天、7天內、30天 - 轉

30個MySQL千萬級大數據SQL查詢優化技巧詳解

[SQL Server玩轉Python] 二.T-SQL查詢表格值及Python實現資料分析

轉：關於SQL查詢效率優化

【雜文】各種技巧彙總

sql server查詢技巧

（轉）資料庫SQL查詢語句大全

常用SQL查詢語句優化技巧總結

SQL資料庫查詢實現行轉列與列轉行結果SQL語句

C# SQL 多條件查詢技巧

MySQL單表查詢優化技巧彙總

sql語句的各種模糊查詢

各種SQL查詢技巧彙總 (轉)

相關推薦