order by clause in sql

write in front of the words: sometimes do not understand the SQL statement parts of the execution order, resulting in a deviation in understanding, or when writing SQL statements, it is necessary to understand the order of execution of SQL statements. Can have time to write

2012-02-07 19:39 First where Condition 1, then group by condition 2 again order by condition 3If a GROUP BY clause is declared, the output is divided into different groups that match one or more values. If there is a HAVING clause, it eliminates those groups that do not meet the given criteria.If the ORDER BY

#{} is equivalent to PreparedStatement in JDBC${} is the value of the output variableYou might say it's unclear, so don't worry. Let's look at the 2 snippet code:String sql = "SELECT * from Admin_domain_location order by?"; PreparedStatement st = con.preparestatement (SQL), st.setstring (1, "domain_id"); System.out.println (St.tostring ());ResultSet rs = St.execu

Order by: when the order by clause is used, in most cases, the specified sorting sequence selects columns, but the sorting column may not select columns. However, if the distinct keyword is used in the select clause, the sorting column must be the selected column. Otherwise, an error is returned. Group by: tells the d

From: Performs a Cartesian product (Cartesian product) (cross join) on the first two tables in the FROM clause, generating a virtual table VT1On: Apply an on filter to VT1. Only those lines that make OUTER (Join): If OUTER join is specified (relative to cross join or (INNER join), the reserved table (preserved table: Left outer join marks the left table as a reserved table, right outer join marks the right table as a reserved table, A full outer join

Absrtact: The application of SqlServer2005 has been developed for some time, but many times it is SqlServer2005 as a SqlServer2000, so many of the new features of SqlServer2005 I did not use, One reason is to be compatible with SqlServer2000 users. The new features will certainly be used in the real world, and to know the new features of SQLServer2005 can be found in the Microsoft website's what ' s New in SQL Server 2005? , there are many features th

Label: SQL Union and SQL UNION ALL usage difference efficiency and the problem with order by and group by mates SQL Union and SQL UNION ALL usage SQL UNION operator The UNION operator is used to combine the result set of two or

For ms SQL Server databases, there are several problems that are easy to misunderstand. For these problems, even if many SQL Server DBAs have incorrect understanding or insufficient understanding, therefore, I want to write a few articles to elaborate on the problems that are easy to understand and make mistakes. I also hope to correct these questions on the Internet (or I may know something wrong, ). The

Requirements: According to the PID field to the data deduplication, sorted according to the sort field, you need to display this two fields.　　　　, which is the original data, sorted first:　　　　After sorting, two items were found to be duplicated, one needed to be removed,　　　　Because distinct to examine each column in the Select, each column that appears must be the same to calculate the duplicate data, and the sorted data inside the same PID data in the same sort value, distinct at this time is in

Label: 1 --Sort 2 --1. Sort by list 3 --2. Sort aliases 4 --3, column position sorting (when using Union,union All,intersect,minus collection operation, the list is different, but want to sort) 5 SELECTDeptno,dname fromDeptUNION 6 SELECTEmpno,ename fromEMP7 ORDER by 1 DESC; 8 --4. Sorting using non-select columns 9 SELECTEname fromEmpORDER bySalDESC; Ten --5, multi-line sorting, first based on the ORDER B

Tags: logic skip ASC Join start ble from using avgExecution order: The parsing order of SQL is from left to right, from top to bottom. (analogy compilation) The official given select query SQL structure is described below: SELECT [All | DISTINCT | Distinctrow] [high_priority] [Straight_join] [Sql_

Label:Order data is generally changed more data, query conditions are more complex, if there is no rule to explain, the change of the interface will be more frequent; because the individual does not like to use stitching SQL in the business side of the way, in addition to doing a safe origin, the business side of SQL splicing easy SQL injection, so do not conside

loaded into the above file.Length () returns string lengths.SUBSTR () intercepts the string substr (string, position, length) substr (Database (), 1, 1).ASCII () returns the ASCII code of the character #通过 >,() Sleep (n) program hangs n seconds. Used for time blinds.if (A,B,C) is the same as A?b:c0X03 the construction of SQL injection statements(1) SELECT column name from table name WHERE conditionSelect Username,password from Users where id=inputSel

Original address:Stairway to SQL Server indexes:level 10,index Internal StructureThis article is part of the SQL Server cable Introduction order series (Stairway to SQL Server Indexes).In the previous level, we introduced the index from a logical perspective, focusing on what they can do for us. Now, it's time to take

Statement selecting records from an Access database is one of the most frustrating things to do in the order in which they are entered in the database. Even if you use sort by to change the view of a record in an access environment, the order of records in the datasheet does not change. If you're using Asprecordset to write records on a Web page, you probably know how painful the

Tags: next soft instance IMA Image Technology Stat member EnterSQL execution OrderReprinted from: http://www.cnblogs.com/knowledgesea/p/4177830.htmlObjectiveDatabase query execution, is undoubtedly one of the programmer's necessary skills, but the process of database query execution is gorgeous and colorful, but it is very rarely understood, today brother to take you to take you fly, deep into the context of this SQL query, for the query performance o

Organizing data in a meaningful way can be a challenge. Sometimes what you need may be a simple sort, but usually you need to do more and you need to group them for analysis and statistics. Fortunately, SQL provides a number of statements and actions to sort, group, and Digest. Some of the tips below will help you identify when to sort, when to group, when and how to count. For more information on each statement and action, see Books Online.1. Use sor

Tags: program string position Comment test result registered user name cap param input dataOne: SQL injection classification SQL injection is generally divided into two categories: first-order SQL injection (normal SQL injection), second-level

Tags: arc requires IDE number Server index execute execution plan log The source of this article: http://www.cnblogs.com/wy123/p/6008477.html For statistics on the number of rows of data estimates, previously written on the non-related columns (separate or separate index columns) of the algorithm, refer to here. 　　Today, let's write the statistical information on the calculation methods and potential problems of the composite index at the time of estimation. The prototype of this paper comes fr

Label:The difference between MyBatis's #{} and ${} and the order by injection problemOriginalHttp://www.cnblogs.com/chyu/p/4389701.htmlForeword a little, straight to the subject. #{} is equivalent to PreparedStatement in JDBC ${} is the value of the output variable In short, #{} passed the arguments with single quotation marks, and ${} passed the arguments without single quotes. You might say it's unclear, so don't worry. Let's look at the 2 snippet c