icnd1 topics

,hiredate,max (Salary) ' highest pay ' from the users WHERE hiredate >= ' 2010-01-01 ' GROUP by Dept,edlevel;SELECT Dept,edlevel,hiredate,max (Salary) ' highest salary ' from the users GROUP by Dept,edlevel have hiredate >= ' 2010-01-01 ';For example: Looking for the highest and lowest salary of a department with more than 2 employeesSELECT Dept,max (Salary) ' Maximum Salary ', min (salary) ' minimum wage ', count (1) ' Number of departments ' from the Users GROUP by dept have count (1) > 2;For

and English examsMulti-table ConnectionSELECT a.* from student a INNER joins score B on a.id = b.stu_id WHERE b.c_name = ' computer ' OR b.c_name = ' English ' GROUP by b.stu_i D having count (b.c_name) = 2;SELECT a.* from student a INNER joins score B on a.id = b.stu_id INNER joins score c on a.id = c.stu_id WHERE b.c_name = ' calculation Machine ' and c.c_name = ' English ';Sub-querySELECT * from student where ID in (select stu_id from score where c_name = ' computer ' and stu_id in (select s

from table1ORDER by ID;OPEN CFETCH NEXT from C to @id, @nameWhile @ @fetch_status =0BEGINSELECT Id,nameFrom table1WHERE [email protected]FETCH NEXT from C to @id, @nameENDCLOSE CDeallocate C4. Create a trigger that requires a record to be inserted into the Vendor table when a record is inserted in the Product tableCREATE TRIGGER SuppliersaddOn ProductAfter INSERTAsINSERT into SuppliersSELECT INSERTED. Supplierid,inserted. Name,inserted. PriceFrom inserted5. Create an inline table-valued functio

method and a stored procedure1, the parameter list of the stored method only allows parameters of the in type, and it is not necessary or allowed to specify the IN keyword2, the storage method returns a single value, the type of the value defined in the head of the stored method3, the storage method can be called inside the SQL statement4, the storage method cannot return a result setGrammar:Create function ([function parameter [,....]]) Returns return typeBeginIfReturn (the returned data)ElseR

data types that are defined as text, image, and bit.How to delete data from millions of levels or more (really good technical text)About indexes: Because indexes require additional maintenance costs because index files are separate files, when we add, modify, and delete data, we create additional operations on the index files that consume additional IO and reduce the efficiency of the increase/change/delete execution. So, when we delete database millions data, query the official MySQL manual to

the employee table, the total wage, the maximum wage, the minimum wage, the average wageSelect COUNT (*), sum (SAL), Max (Sal), Min (sal), avg (SAL)from EMP;--7, find information about employees and your department--Descartes ProductSELECT * FROM Emp,deptwhere Emp.deptno = Dept.deptno;--8, query employee information and the department's information, request to have no staff of the department also to show outSELECT * FROM Emp,deptwhere Emp.deptno (+) = Dept.deptno--9, query employee information

problem from the script itself to break through it is not very difficult. But we can indirectly "fix" the network from some external means. Now the combination of iis+asp+sql2000 is more common. and a Web site using a large number of ASP script programs, it is inevitable that there is no mistake. If there is a SQL injection point on a host, and this host is installed with the mobile network SQL version, it is basically possible to conclude that the mobile network is yours. Let's take a look at

, eliminate sequential access to large table row data, index connected columns, and use unions to avoid sequential access. Although there are indexes on all the check columns, some forms of where clauses force the optimizer to use sequential access. The following query forces a sequential operation on the Orders table: Select *from orders where (customer_num=104 and order_num>1001) or order_num=1008 although the customer Indexes are built on _num and Order_num, but in the above statement the opt

' @ '% ' (using Password:no)11 Restricting permissionsThe ability to grant usage restrictions to users, such as the ability to query the database 5 times per hour.Mysql> Grant Select on test.* to [email protected] '% ' with max_queries_per_hour 5;There are 3 other parameters Max_updates_per_hour, Max_connections_per_hour, Max_user_connections, respectively, to update the number of MySQL per hour, The number of connections to MySQL per hour and the maximum number of users per hour, assuming 0, m

, average scoreFrom (SELECT S#,avg (score) average score from SC GROUP by s#) T2ORDER by average grade desc; 14. Check the records of the top three grades of each section: (regardless of the performance of the situation)SELECT t1. s# as student id,t1. C # as course Id,score as fractionFrom SC T1WHERE score in (SELECT TOP 3 scoreFrom SCWHERE t1. c#= C #ORDER by score DESC)ORDER by T1. C #; 15. Check the top two of the best results for each doorSELECT t1. s# as student id,t1. C # as course Id,scor

resources or data, not code, including static local variables, global variables, shared data structures, caches, linked lists, red and black trees, and various forms of resource data.The following are the chapters of this topic:Linux Concurrency and Synchronization topic (1) Atomic operations and memory barrierLinux Concurrency and Synchronization topic (2) spinlockThe Linux Concurrency and Synchronization feature (3) SemaphoreLinux Concurrency and Synchronization topic (4) Mutex mutexLinux con

representation of polymorphism between a parent class and a subclass, and overloading overloading is a representation of polymorphism in a class. If you define a method in a subclass that has the same name and arguments as its parent class, we say that the method is overridden (overriding). When an object of a subclass uses this method, the definition in the subclass is called, and for it the definition in the parent class is "masked". If more than one method with the same name is defined in a

manufacturer puts the buffer memory into the device to reduce access latency and adapt to the performance of the host controller. In this way, the host controller can perform overlapping operations on multiple devices at the same time, and the figure shows this overlap process. On the other hand, caching uses more complex intelligent technologies to determine what data it will store. Buffer is composed of relatively simple memory chips which are constantly detached and filled, but the disk ca

This article original from Http://blog.csdn.net/voipmaker reprint annotated source.The WebRTC-Peer part uses the ice framework, the ICE framework includes the Stun,turn, and one problem with the actual use of WebRTC to develop audio and video applications is that calls are built very slowly because the ice process takes too much time for the client to communicate with the stun server before initiating the call The server reflexive address and the relay address, together with the local host addre

simplify the work of millions of Java programmers by adding scripting languages to Java. Java programmers don't have to write a whole bunch of test cases or drivers for a class they just wrote.Jython provides most of the functionality of Python, as well as the ability to instantiate Java classes and interact with Java classes。 The Jython code is dynamically compiled into Java bytecode, so you can extend the Java class with Jython. You can also use Java to extend Python. It is easy to write a c

compilation, that is, constant values are replaced with initialized values; readonly-Modified constants are deferred until run timeIn addition, const constants can be declared either in a class or within a function body, but static ReadOnly constants can only be declared in a class.In 4.c#, the difference between a value type and a reference typeAll value types in C # are implicitly derived from System.ValueType:Value types: Sbyte,byte,short,int,long,datetime,ushort,unit,ulong,char,float,double

Myth free download and special topics Information Source: delphiscn blog Movie name: the myth)Video type: action moviesStarring: Jackie Chan, Liang Jiahui, Jin Xishan (Korea), Marica (India), SUN Zhou, Shao BingMajor actors: Yu rongguang, Shi Xiaolong, and Xu Jinjiang [Film Introduction] Love, greed, betrayal, and struggle have never changed the history of mankind for thousands of years. At the invitation of William (Liang Jiahui ornaments), Jack (Ja

Let's talk about some interesting topics about object-oriented theory. The story of squares and rectangles Square is a special.----He In the discussion of object-oriented theory, there is a very confusing question: why cannot a square be derived from a rectangle? Because from the definition of geometric mathematics, a square is a rectangle, a special rectangle.First, let's look at the encapsulation of the rectangle. There are many kinds of rectangular

Silverlight shares a set of enterprise development topicsSilverlight default theme for a long time, but also visual fatigue, so the internet to find the next Silverlight theme. There are not many themes found in SL, the following jetpack theme is SL4 era release, but SL5 can also use. For enterprise development also good, who has better, also told me:) Download and install: http://www.microsoft.com/downloads/en/details.aspx?FamilyID=e9da0eb8-f31b-4490-85b8-92c2f807df9edisplaylang=enThis bag ac

is a cache avalanche? How to avoid?Cache penetrationThe general cache system is to follow the key to cache the query, if there is no corresponding value, it should go to the backend system lookup (such as DB). Some malicious requests will deliberately query the nonexistent key, the volume of the request is very large, it will cause great pressure on the back-end system. This is called cache penetration.How to avoid it?1: The case of NULL query results is also cached, the cache time is set a lit