Programmer Group

All along, I think it's very easy to use the \ G parameter in MySQL to change the display mode of the output result set, especially in the command-line interface. But ORACLE database doesn't have this function. Today, when I searched a blog post of master Tom, I found that master used a stored procedure, print table, to implement such functions ...

4. Joint query of Table 4: student course selection query Question and Description: Students and achievement table students are the main table and achievement is the sub table Curriculum and score table curriculum is the main table and score is the sub table Teacher and curriculum teacher are the main table, curriculum is t ...

There are a lot of garbage data in the table. Now delete and keep one of them (whether to judge repeatedly is based on multiple fields) Scenario 1: DELETE FROM vitae a WHERE (a.peopleId, a.seq) IN ( SELECT peopleId, seq FROM vitae GROUP BY peopleId, seq HAVING count(*) > 1 ) AND rowid NOT IN ( ...

jar package required for connection pool configuration Servlet api.jar imports the jar package under Tomcat directory by itself. If there are no other jar packages See download link ----- > download (there's no way to set it as free, set it as the lowest point to download) Download portal 2: YouDaoNote These jar packag ...

Oracle storage functions The storage function is also a named PLSQL block. --Note: the stored procedure has no return value, but the stored function has a return value. The difference between stored procedure and stored function Generally speaking, the difference between a procedure and a function is that a function can ...

JDBC concepts and quick start cases 1. Concept of JDBC: Operate database by Java code (add, delete, modify, check) 2. Quick start procedure: A.Import jar package B.Registration driven Class.forName("com.mysql.jdbc.Driver"); C.Acquisition drive String url = "jdbc:mysql://127.0.0.1:3306 / EE "; / / EE is the name ...

PHP realizes the effect of similar question bank Hello everyone, I think someone is back. I learned a little bit about PHP recently, and then I want to write a simple example to try. So I wrote something similar to extracting questions from the question bank, which is to input the number of questions to be extracted first, and then randomly ext ...

The most common way to connect to the database is through string connection, as follows: public static string connstr = "server = localhost; uid = root; pwd = 123456; database = db_sms;"; MySqlConnection conn = new MySqlConnection(connstr); MySqlCommand comm = new MySqlCommand(sqlstr, conn); However, this method is not con ...

I. demand. Existing user table, user role table, role table. One of the users corresponds to multiple roles. When querying user details, you need to directly query the role names of users, separated by commas. 2, sql table creation script 2.1 user table CREATE TABLE `user` ( `uid` bigint(20) NOT NULL AUTO_INCREMENT COMMEN ...

Learning content Use of JDBC Development steps 1. Select database: load database driver; 2. Connect to the database 3. Create database query 4. Get query results 5. Get query results Complete JDBC operation code package com.dodoke.jdbc; import java.sql.Connection; import java.sql.DriverManager; import java.sql.Prepared ...