Label:Recently encountered a more interesting problem in the project, the online search for some methods, summarized here to share. We often encounter such a scenario: the need to query data, there are some query conditions, but when the query, we hope that when a condition is empty, then do not filter this condition, the main idea is to deal with the following:
http://blog.csdn.net/sxdtzhaoxinguo/article/details/51481430Abstract: MySQL database implementation of paged query SQL statement writing!One: Paging needs:The client passes the start (page number), limit (number of bars per page) two parameters to page through the data in the database table, then we know that the MySQL database provides paging function limit m,n, but the use of this function is different fr
SQL Server paging query processing method summary, SQL Server Paging
Sqlserver2008 does not support the keyword limit, so its paging SQL query statement cannot be performed using MySQL. Fortunately, sqlserver2008 provides top, rownumber, and other keywords, in this way, you
), variable length, can hold photos, files, etc.
int, integer field. Example: Userage int
float, floating-point data is approximate. Example: Userresults float, the approximate numeric data type used to represent floating-point numeric data.
datetime, Date type. Example: Createdatetime datetime
Bit, Boolean type. Can be set to True is male, false is schoolgirl
If the content is very much, indeterminate length (such as article), can be used: nvarchar (max) 6. Save the tabl
$ SQL = "select count (qid) from test_querys where istested = 1And qid Qid from $ left_cr where issubmit = 1 and qid $ SQL = "selectCount (A. qid) from test_querysA left join (select qid from $ left_cr where issubmit = 1 and rankval = 1 and qid
1. The first query takes 2.9 s, and the second query takes 0.2 s! Use in
1T-SQL Simple query statement2 3 Simple query:4 51.The simplest query (check all data)6SELECT * from table name; NOTE: *represents all Columns7SELECT *From info8 92.querying a specified columnTenSelect Code,name from Info One A3.Modify the column name of the result set -Select Code as' Code ', name asNameFrom info -
SQL query (Note 2--entity query)Second, the entity queryIf the query returns all of the data columns for a data table, and the data table has a corresponding persisted class map, we convert the query results into entity queries. You can use the multiple overloaded addentity
Label:The first is the problem of fuzzy query, I started with the following conditions: SELECT * from the user where name like '% #value #% '. But how can not, as if also reported wrong. Later on the internet found a solution, is to use $ to replace the # number.1> write: Like '% $value $% ' can be,2> also found another method, but that method I tried for a long time, is not, the method is: like '% ' | | #value # | | '% ', the
Label:Write in front: This is the first T-SQL query Advanced series article. But the T-SQL query step-up series is far from finished. This topic is advanced and I think it is because this topic requires some advanced knowledge as the basis. If there is any mistake in the article, please do not hesitate to correct me. T
[Name],subject,score Here for a good understanding only one column to get the following results With the example of the language accomplishment line train, it is easy to add the other two columns, Select [Name],Chinese =caseWhen subject= ' language ' then score else 0EndMathematics =caseWhen subject= ' math ' then score else 0EndForeign Language =caseWhen subject= ' foreign language ' then score else 0EndFrom StudentscoreGroup BY [Name],subject,score The following is the result of the
When converting Oracle queries to SQL queries, you need to pay attention to a lot of issues. The following gives you a detailed analysis of the number trade-offs in converting Oracle queries to SQL queries for your reference.
Number trade-offs
Oracle Database has a TRUNC function, which returns n digits of the m-bit decimal number. If m is omitted, n is 0 digits. The m value can be negative, indicating th
Tags: style blog http color io ar for strong SPSQL query table, all field names of the table2011-07-29 10:21:43|Category: SQL Server | Tags: table sql fields | Report | Font size Subscription SQL query table, all field names of the tableSQL SERVERView all table nam
The instance resolution and SQL horizontal display are displayed in the row-to-column manner of SQL query statements.
This article shares two examples of horizontal display of rows and columns in SQL query statements for your reference. The specific content is as follows:
Ex
1. Use SET STATISTICS TIME ON
-- First clear the cache
Dbcc dropcleanbuffers;
Dbcc freeproccache;
-- Run
Set statistics time on;
SELECT orderid, custid, empid, shipperid, orderdate, filler
FROM dbo. Orders
WHERE orderdate> = '123'
AND orderdate
Set statistics time off;
GO
You will get a similar message:
SQL Server Analysis and Compilation Time:
CPU time = 15 ms, occupied time = 33 Ms.
SQL Server executi
Before: This is the first T-SQL query advanced seriesArticleBut the advanced series of T-SQL query is far from finished. I think this topic needs some advanced knowledge as the foundation. If there are errors in this article, please do not correct it. The content of this article requires the indexing knowledge as the b
,-1, GETDATE ()),111)//111 is the style number, (100-114)Query first day of the month Date: Select DATEADD (mm, DATEDIFF (mm,0, GETDATE ()),0) asfirstday Query Last day of the month Date: Select DateAdd (MS,-3, DATEADD (mm, DATEDIFF (M,0, GETDATE ()) +1,0)) asLastday//change-The value of 3 changes accordinglyHow many days are there this month:SelectDatePart (Dd,dateadd (dd,-1, DateAdd (MM,1, Cast ((CAST (GE
Hibernate native SQL query, Hibernate native SQL
Recently, a more complex query was made, and the basic query of hibernate could not meet the requirements. Therefore, we had to use the native SQL
SQL subquery, multi-Table query, and joint Query
Subquery, multi-Table query, and joint QueryThese three concepts are interpreted slightly differently in different SQL versions, roughly as follows:
JoinYou can check related SQL
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