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Tags: query field reason expression Image user Rac dual strongabout Oracle 1. Sqlplus Connect Remote Oracle Command Sqlplus (need to set environment variables) Scott (username)/5456 (password) @192.168.230.128:1521 (IP)/ORCL (database name) 2. View Current User Show user--Sqlplus command 3. View the table under the current user SELECT * from tab; 4. Execute the previous SQL statement /--Sqlplus command Table Operations 1. View Emplo

Tags: MySQLThis article mainly introduces the query syntax of MySQL in Where,group by, order BY, Limit,join,union, union All, child table and so on.Test data preparationCREATE TABLE EMP (empno numeric (4) NOT NULL, ename varchar, job varchar (9), Mgr Numeric (4), hired Ate datetime, Sal numeric (7, 2), Comm Numeric (7, 2), Deptno numeric (2)); CREATE TABLE Dept (deptno Numeric (2), dname varchar, loc varchar (13)); CREATE TABLE Salgrade (grade nume

Tags: sele common union Name list ble har specify order BYCommon SQL query statements are as follows: First, simple query statements 1. View table structure SQL>DESC EMP; 2. Querying all Columns Sql>select * from EMP; 3. Querying a specified column Sql>select empmo, ename, Mgr from EMP; Sql>select DISTINCT Mgr from EMP; Show only items with different results 4. Querying a specified row Sql>select * from emp WHERE job= ' clerk '; 5. Using an arithmetic expression Sql>select ename, SAL*13+NVL (

Function-based indexesA function-based index is an index that stores a pre-computed function or expression value. These expressions can be an arithmetic expression, an SQL or a/PL function, a C call, and so on. It is worth noting that the general user to create the function index, must have the global QUERY rewrite and create any index permission. Otherwise, you cannot create a function index, see the following example:Example 1: Index of the uppercase conversion function for the ename column o

, points.points from names INNER JOIN points on Names.name=points.nameB. SELECT names.name, Names.number, points.points from names full OUTER JOIN points on Names.name=points.nameC. SELECT names.name, Names.number, points.points from names to OUTER JOIN points on Names.name=points.nameD. SELECT names.name, Names.number, points.points from names right OUTER JOIN points on Names.name=points.name 4. Given StaffID INTEGERName CHAR (20)Dept INTEGERJob CHAR (20)Years INTEGERSalary DECIMAL (10, 2)

First, simple query statements1. View table structureSQL>DESC EMP;2. Querying all ColumnsSql>select * from EMP;3. Querying a specified columnSql>select empmo, ename, Mgr from EMP;Sql>select DISTINCT Mgr from EMP; Show only items with different results4. Querying a specified rowSql>select * from emp WHERE job= ' clerk ';5. Using an arithmetic expressionSql>select ename, SAL*13+NVL (comm,0) from EMP;NVL (comm

Using the EMP and dept tables under the Scott user--(1) To inquire all employee information of 20 department door.SELECT * from EMP where deptno=20;--(2) To inquire the employee number, employee name and department number of all employees who work for clerk. (Note case)Select Empno,ename,deptno from emp where upper (Job) = ' Clerk '--(3) query bonus (COMM) employee information that is higher than the salary (SAL).SELECT * FROM EMP where

-computed function or expression value. These expressions can be an arithmetic expression, an SQL or a/PL function, a C call, and so on. It is worth noting that the general user to create the function index, must have the global QUERY rewrite and create any index permission. Otherwise, you cannot create a function index, see the following example:Example 1: Index of the uppercase conversion function for the ename column of the EMP table idx:CREATE INDEX idx on EMP (UPPER (ename));This allows you

hand, you can simulate your computerTwo different serial devices. Usually the panel behind the computer host provides two 9-pin serial port, please put these two serial portsThe 2,3,5 foot is connected by the method described earlier. The electronic market has ready-made connection head to sell, please do not buy that kind of packageTight joints, and to buy with a screw package can be opened the connector, so that you can easily use the need to connectConnect each stitch.Comm API BasicsI am not

SQL statement for SQL profile tracking.the injected code is as follows: Select COUNT (*) from Users where Password = ' a ' and UserName = ' B ' or 1=1-' Here someone set username for "B ' or 1=1–". The actual execution of SQL becomes the following: It is clear that SQL injection was successful. Many people know that parameterized queries can avoid the injection problems that occur above, such as the following code:Class Program {private static string connectionString = "Data source=.;i Nit

"Description: "%" this wildcard matches characters of any length.SELECT * from Stu where sname like ' z% ';3.4 Check the student record of the 2nd letter "I" in the nameSELECT * from Stu where sname like ' _i% ';3.5 Student records with the letter "a" in their nameSELECT * from Stu where sname like '%a% ';//-----------------------------------------------------------------4.1 Removing duplicate recordsKeywords:distinct = Remove duplicate query result records.Select Gender from Stu; A large number

completely delete the e table, purge recyclebin is required. You can also drop table e purge in two steps; after table e is deleted, scott does not have its records.) SQL-> drop table e purge; 6. Update the test table to set the ID number of a student named 'li _ si' to 3. 7. Add the bonus (comm) of each employee in the emp table to 500. SQL> update emp set comm = nvl (