Multiple Table Operation of SQL Statements

Before talking about multi-table queries, make a requirement that is not related to multi-table queries. Suppose you have such a column of IDS in Table B +------+ | id | +------+ | 1 | | 2 | | 1 | | 3 | | 4 | | 5 | +------+ Please indicate the serial number for the id column according to the query in table B and displa ...

Posted by moboter on Thu, 23 May 2019 02:46:21 +0200

Wpf Excel Import and Export Data

Turn: http://blog.csdn.net/sanjiawan/article/details/6818921 Microsoft's import and export methods are basically the same whether they are asp.net, winform, or wpf. It's all about instantiating Excel classes, creating workbooks, creating worksheets, and then saving or extracting data. So easy to operate that feeling has become a matter of cou ...

Posted by jacobelias on Thu, 23 May 2019 00:23:56 +0200

DBCP: One of the Open Source Data Sources

What are the advantages of using connection pools over our usual JDBC code? 1. Resource reuseBecause of the reuse of database connections, frequent creation is avoided and a large amount of performance overhead caused by connections is released. On the other hand, it also increases the stability of system operation environment on the basis of ...

Posted by nascarjunky on Wed, 22 May 2019 22:58:54 +0200

MySQL Introduction Basic Grammar 1

I. Basic Use of MySQL 1.1 Basic operations on the command line Mysql-u username-p carriage return Enter password: xxx Enter the database (All commands in mysql end with a semicolon and enter help; query all mysql commands) 1.2 MySQL directory structure bin: All executable files exe File of MySQL InstanceConf ...

Posted by bruce080 on Wed, 22 May 2019 20:15:30 +0200

Analysis of SQL in a hang database

Someone at the interface came to me and said that there was a stored procedure that couldn't run and tried to report errors several times. ORA-12801: Error signal in parallel query server p001, instance xx ORA-04030: Insufficient process memory when attempting to allocate 16328 bytes (xxxx) It also monitors the receipt of spatially increasi ...

Posted by mxdan on Sun, 19 May 2019 22:34:38 +0200

oracle database index related knowledge

1. Index: Two new tables, T1 and T2, are created as follows: When both tables are queried the same way, the T1 table uses an index, but the T2 table does not scan the full table. select * from t1 where id=10; select * from t2 where id=10; This is mainly because the values of the clustering factor in the T1 table ...

Posted by ozzmans on Sun, 19 May 2019 11:42:35 +0200

DML for (MariaDB/MySQL): Data Update, Delete

Contents of this article:1.update statement2.delete statement 2.1 Form Delete 2.2 Multi-table Deletion3.truncate table 1.update statement update is used to modify records in a table. # Form update syntax: UPDATE [LOW_PRIORITY] [IGNORE] table_reference [PARTITION (partition_list)] SET col1={expr1|DEFAULT} [,col2={expr2|DEFAULT}] ...

Posted by thomashw on Sun, 19 May 2019 09:27:22 +0200

Java Develop - MySQL-based SQL protocol/optimized record

1.SQL protocol 1. Statute of Forms Required three fields: create table `demo` ( `id` bigint(32) not null auto_increment comment 'Primary key', `gmt_create` timestamp not null default current_timestamp comment 'Active Creation Time', `gmt_modified` timestamp not null default current_timestamp on update current_timestamp comment 'Passiv ...

Posted by AndyB on Sat, 18 May 2019 13:07:56 +0200

ORA-01779: Cannot modify columns corresponding to non-key saved tables

Today, Zhongshan company lets the dispatching arrangement batch be seen remotely, because it is the same source program, making the formal library will not report errors, making the test library will report errors, thinking of the problem of data or database settings, so it debugs the source program, and the program will report errors when it c ...

Posted by RedRasper on Sat, 18 May 2019 05:25:08 +0200

Let's talk about Java 8 Stream features

The Java 8 API adds a new abstraction called Stream, which allows you to process data in a declarative manner. Stream provides a high-order abstraction of Java set operations and expressions using an intuitive way similar to querying data from a database with SQL statements. Stream API can greatly improve the productivity of Java program ...

Posted by jesse_james on Thu, 16 May 2019 13:47:26 +0200