SQL Server top keyword usage

Sometimes it is not necessary to retrieve all the data for query , When we only use some of them , You need some keywords .

MYSQL The key word is limit,SQL server The key word is top.

 SQL server top Use of keywords ：

# Take out the first three items of data 
select top 3  * from table

# Take out the top percent of the data 20
select top 20 percent * from table

# From the query 200 Strip of data 30-100 Data 
with t as ( select top 200 row_number() over(order by uuid) r, * from table)
select * from t where r between 30 and 100

# From the query 200 Strip of data 100 Data after 
with t as ( select top 200 row_number() over(order by uuid) r, * from table)
select * from t where r >100

MYSQL limit Use of keywords

# The meaning is to skip 2 Strip out 1 Data ,limit The back is from 2 Start reading , Read 1 Bar information , That is, read the 3 Data 
select * from table limit 2,1;                 

# The meaning is from 1 strip （ barring ） The data starts to come out 2 Data ,limit It's followed by 2 Data ,offset The back is from 1 Bar start reading , That is, read the 2,3 strip 
select * from table limit 2 offset 1;      

MYSQL limit Use of keywords

/*Mysql limit offset Example 
 example 1, Suppose the database table student There is 13 Data .
*/

# Code example :
//  sentence 1 and 2 All return to table student Of the 10、11、12、13 That's ok   
 sentence 1：select * from student limit 9,4
// sentence 2 Medium 4 Said to return to 4 That's ok ,9 Indicates starting at line 10 of the table 
 sentence 2：slect * from student limit 4 offset 9


 example 2, adopt limit and offset  Or only through limit Paging function can be realized .
 hypothesis  numberperpage  Indicates the number of items to be displayed on each page ,pagenumber Page number , that   Back to page pagenumber page , The number of entries per page is numberperpage Of sql sentence ：
 Code example :
 sentence 3：select * from studnet limit (pagenumber-1)*numberperpage,numberperpage
 sentence 4：select * from student limit numberperpage offset (pagenumber-1)*numberperpage

Other database related contents

-- If I find out 1000 Bar record , I want to take the first 200～300 Bar record 

--oracle:
with t as ( select rownum r, * from  surface  where rownum<=300 )
select * from t where r>=200

--db2:
with t as ( select row_number() over(order by  Field ) r, * from  surface  fetch frist 300 rows only)
select * from t where r>=200

-- among  sqlserver\oracle\db2 Or directly 
with t as (select row_number() over(order by  Field ) r, * from  surface )
select * from t where r between 200 and 300