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max_click as select max as
From code
Group by kind;
2. Filter to ensure only one record per category
Select *
From (Select id,kind,click_num
From code
where click_num = ( Select b.click_num
From max_click as b
where code.kind = B.kind
)
) as a
Group by kind;
Normal operation, speed 0.78 seconds. (altogether 23,000 data in the table) okay! Done! the first SQL
There is a forum to see a post, " Consult the query out of the continuous date record method", screenshot as follows:
Insus.net tries to write a program and test it to get the expected results, which can be referenced and learned by SQL code.
Copy Code code as follows:
--Create a temporary table that will store records for consecutive dates
Original: SQL statement tip: Query for data records that exist in one table and not in anotherMethod One (only for single fields)Easy to understand, low efficiency with not inSelect a.ID from A where a.id not in (select ID from B)Method Two (for multiple field matches)Use left Join...on ..., "b.ID isnull" indicates a record in which the b.ID field is null after t
, there is no one-cut means to solve all the problems.Summarize:In this paper, a simple example is given to analyze the effect of the order of columns on the query when creating a conforming index.Note that when creating an index, you should not only consider which columns to create indexes on, but also whether the order of indexed columns will affect the query.Avoid talking about indexing, which is the "Index on
SQL statement query table name/column name/primary key/Auto grow value in database
----A table created by a user in a query database
----JSJ01 as database name
Select name tablename from JSJ01. sysobjects where type= ' U ' and name not in (' dtproperties ')
--field information in the
Tags: sel over l database query sort name Statement data rankNow there is a table as followsId Name Age classify score1 1181 Class 122 2,172 class 193 3,193 Class 30I'm going to rank them according to their scores. Create a new column store sort valuesThe->sql statement is as followsSelect Row_number () over (order by score ASC) as Number,id,name,age,classify,sco
CREATE TABLE Students (course varchar), Stu_name varchar (TEN), City varchar (ten), score int INSERT into students values (' math ', ' Jack ', ' Tianjin ', ' n '), insert into students values (' math ', ' Jordan ', ' Tianjin ', 80); INSERT into students values (' math ', ' James ', ' Beijing ', ' n '), insert into students values (' English ', ' Jack ', ' Tianjin ', ' n '); insert into students values (' English ', ' Jordan ', ' Tianjin ', max), insert into students values (' English ', ' James
Label:pivotextraalt==time tweenrocexepat 1 use [aps_future_ft] 2 GO 3/****** object:storedprocedure [dbo]. [A_crudeprice] Script DATE:2013/11/5 19:13:21 ******/4 SET ANSI_NULLS on 5 go 6 SET QUOTED_IDENTIFIER on 7 Go 8--=============== ============================== 9--Author: T-SQL row to column, database query paging
SELECT * FROM (Select ' Finish_order_info ' as Table_name,count (1) as Num from Fraudorder.finish_order_info where Crt_dt between To_date (' 2014-12-24:00:00:00 ', ' yyyy-mm-dd,hh24:mi:ss ') and to_date (' 2014-12-25:00:00:00 ') group BY ' Finish ' UNION ALLSelect ' Discard_order_info ' as TABLE_NAME, COUNT (1) as Num from Fraudorder.discard_order_info where Crt_dt between to_date (' 2014-12-24:00:00:00 ', ' yyyy-mm-dd,hh24:mi:ss ') and to_date (' 2014-12-25:00:00:00 ') union ALLSelect ' Raw_air
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