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MySQL Statement basic simple querySection I.--or # single-line comment/*** Multi-line Comment*/--C CREATE DATABASE examCREATE DATABASE Exam;Use exam;/* Create a departmental table */CREATE TABLE Dept (Deptnoint PRIMARY KEY,Dnamevarchar (50),Loc VARCHAR (50));/* Create an employee table */CREATE TABLE EMP (Empnoint PRIMARY KEY,Enamevarchar (50),Jobvarchar (50),Mgrint,Hiredatedate,Saldecimal (7,2),COMM DECIMAL (7,2),Deptnoint,CONSTRAINT fk_emp FOREIGN K

Group functions: Processing a set of data, returning a value for each set of data Common group functions: Count () avg () max () min () sum () Count () function1. Count (*): Returns the total number of rows without removing null values2. Count (column): Returns the number of non-null rowsSelect from EMP; Count (*) Count (SAL) count (COMM)------------------------------- 43. Except for the count (*) exception, the other group

1. Select * from EMP; 2. Select Empno, ename, job from EMP; 3. Select empno number, ename name, job work from EMP; 4. Select Job from EMP; 5. Select distinct job from EMP; 6. Select distinct empno, job from EMP;Note: Because the employee number is not duplicated, it is not possible to eliminate duplicate columns by proving that all the columns are not duplicated at this time. 7. Query the employee's number, name, work, but display the format: 7369 employee, name is: Smith, work is: clearSe

Label:querying an existing database: select name from V$database;Unlock users Scott:alter user scott account unlock; Normal user connection: Conn Scott default password: Tiger General Administrator: System/system Super admin: Sys/sysdisconnecting: DisconnectCurrent User: Show user View all objects under the user: the SELECT * from Tab;dual table is a virtual table within Oracle, with many magicalsingle-line functionFuzzy Query% represents 0 or more characters _ represents a character for a speci

result is displayed: This is the SQL statement tracked by the SQL profile. The injection code is as follows: select COUNT(*) from Users where Password = 'a' and UserName = 'b' or 1=1—' Here, someone sets UserName to"B 'or 1 = 1-". The actual executed SQL statement is changed to the following: We can see that SQL injection is successful. Many people knowParameterized QueryThe above injection problems can be avoided, such as the following code: Class Program {private static string connect

connstring = configurationsettings. receivettings ["connstr"];Sqlconnection conn = new sqlconnection (connstring );Sqlcommand comm = new sqlcommand ("pagination3", Conn ); Comm. Parameters. Add (New sqlparameter ("@ tblname", sqldbtype. varchar); // table nameComm. Parameters [0]. value = tblname;Comm. Parameters. Add (New sqlparameter ("@ strgetfields", sqldbt

With the popularity of Ajax, Ajax is now widely used in projects. It can be said that AJAX is widely used. It is difficult to manage because of a large number of Ajax requests. As a result, we often send requests in a unified manner, with a unique page or portal. So there are the following similarCode: Public Partial Class Ajax: system. Web. UI. Page { Protected Void Page_load ( Object Sender, eventargs e ){ String Comm = request ["

: The authentication method must be "forms" (Authentication mode = "forms "). Add a custom provider named accessmembershipprovider by using the When the requiresquestionandanswer attribute is set to true, it indicates that the question and answer to be answered must be entered during new registration. Connectionstring, indicating the connection string for database connection. Defaultprovider attribute, indicating which provider is used by the system by default, because multiple provid

command Using (Sqlitecommand comm = Conn. createcommand ()) { // Open Database Link Conn. open (); // Insert data Comm. commandtext = " Insert into [T] values (10, 'Hello 9 ') " ;Comm. executenonquery (); // Update Data Comm. commandtext = " Update [T] Set Name = 'Hello 10' where id

are directories, recursion applies to each file and directory. 1.2 comm syntax: comm [-123] file1 file2 note: this command compares two sorted files. File1 and file2 are sorted files. Comm reads the two files and generates three output columns: only the rows that appear in file1, only the rows that appear in file2, and the rows that exist in both files. If the f

% ';3.5 query student records whose names contain the letter ""Select * from stu where sname like '% a % ';//-----------------------------------------------------------------4.1 remove duplicate recordsKeywords: distinct => remove duplicate Query Result Records.Select gender from stu ;=> a large number of repeated records appearSelect distinct gender from stu; => remove duplicate records4.2 view the sum of the employee's monthly salary and CommissionSelect sal * 12 +

1. Without GUI1.1 diff Diff can compare two foldersSyntax: diff [Option] file1 file2 Description: This Command tells you which lines of file1 and file2 need to be modified to make the two files consistent. If "-" is used to represent file1 or fiie2, it indicates the standard input. If file1 or file2 is a directory, diff compares the files with the same name in the directory. Example: diff/usr/xu mine The options are as follows: -B ignores the spaces at the end of the line, and one or more space

Makefile and makefile are equivalent. $ MV makefile $ Make Gcc-C main. c Gcc-C Liu. c Gcc-C generatedatafile. c Gcc-G main. O Liu. O generatedatafile. O-o Liu -L/usr/local/MySQL/lib/MySQL-lmysqlclient-LZ Rm-f *. o Makefile format Depend MAKEFILE file format -------- use the section (rule) as the basic structure $ Cat makefileLibs =-L/usr/local/MySQL/lib/MySQL-lmysqlclient-LZALL: LiuCleanTwo sections of all dependLiu: Main. O Liu. oGeneratedatafile. oLiu dependGcc-G $? -

Increase://get the data on the WinForm firstSqlConnection conn =NewSqlConnection (Dbhelper.strconn); Try{Conn. Open (); stringsql =string. Format (@"INSERT into [dbo]. [Body] ([Danwei],[name],[junxian],[ruwu],[beizhu],[jiguan],[hunfou],[laidui]) VALUES (' {0} ', ' {1} ', ' {2} ', ' {3} ', ' {4} ', ' {5} ', ' {6} ', ' {7} ')", Danwei, name, Junxian, Ruwu, Beizhu, Jiguan,hunfou,laidui); SqlCommand Comm=NewSqlCommand (SQL, conn); intCount

query Syntax:Select *| column name from table name where condition;9. Comparison operators> Greater than= equals>= greater than or equal to! = or 10.IS null and is NOT NULLFind employees who can get a monthly bonusSelect Empno,ename,comm from EMP where comm are NOT null;Inquire about employees without bonusesSelect Empno,ename,comm from emp where

Select Basic Query statementBasic query statements using tables from the Scott user in OracleSELECT * from EMP;--The number of the employee who listed the position as manager, name--Select Empno,ename from emp where job = ' MANAGER ';--like Fuzzy Query I don't know, either.SELECT * from EMP WHERE ename like '%*_% ' ESCAPE ' * ';--Finding employees with bonuses above their salariesSELECT * FROM EMP where comm>sal;--Find out the sum of each employee's s

minimum value from EMP;(3) To find out the total number of employeesSelect COUNT (*) as total number from EMP;(4) Query department number (remove duplicates)Select COUNT (Distinct DEPTNO) as sector number from EMP;(5) Row to columnSet line widthSet Linesize 200Name of employee in Col Department for A60Select Deptno as department number, the name of the employee in the Wm_concat (ename) as department from the EMP Group by DEPTNO;(6) Grouping function and null valueA, the average salary of the st

Tags: performance comm foreground position stage merge type Insert GlobalIndex, index creation, modification, deletion2007-10-05 13:29 Source: User reviews 0 Views 2986IndexAn index is an object in a relational database that is used to hold each record, and the main purpose is to speed up the reading speed and integrity checks of the data. Indexing is a highly technical and demanding task. Generally in the database design phase with the database struc

Routine collection of commonly used SQL query statements and SQL statements Common SQL query statements are as follows: 1. Simple query statements 1. view the table structure SQL> DESC emp; 2. query all columns SQL> SELECT * FROM emp; 3. query specified Columns SQL> SELECT empmo, ename, mgr FROM emp; SQL> SELECT DISTINCT mgr FROM emp; only items with different results are displayed 4. query the specified row SQL> SELECT * FROM emp WHERE job = 'cler '; 5. Use arithmetic expressions SQL> SELECT en

name), MIN (column name) 5.2 NVL (exp1, exp2) If exp1 is NULL, exp2 is used. Same as isNull () in SQL Server. Example: Calculate the income of each person in the emp table (salary + bonus) SELECT sal + NVL (comm, 0) FROM emp; Note: SELECT t. *, rownum from emp t order by sal + NVL (comm, 0 ); Use the ROWNUM semicolon before sorting. The result will cause ROWNUM confusion. 5.3 NVL (exp1, exp2, exp3) If exp1