Basic knowledge of Java ——JDBC
Author: Nobody
Source: CSDN
Original text: https://blog.csdn.net/h1025372645/article/details/89191301
JDBC
Java DataBase Connectivity,java database connection, in order to reduce the difficulty of operating data, java provides jdbc, according to the characteristics of java object-oriented, many operations are encapsulated.
JDBC ...
Posted by arctushar on Wed, 08 May 2019 21:57:03 +0200
MySQL: SQL optimization - commonly used SQL optimization
I. Mass insertion of data
MyISAM table insertion optimization, insertion before closing index updates.
alter table xxx DISABLE KEYS; -- Turn off index updates
... -- insert data
alter table xxx ENABLE KEYS;
Insertion optimization of InnoDB tables:
1) The imported data is arranged according to the p ...
Posted by blues on Wed, 08 May 2019 20:24:04 +0200
[Reload, Organize] Turn on archive mode, archive log is full
At ORACLE10g and 11g versions, the default log archive path for ORACLE is the flash-back recovery area ($ORACLE_BASE/flash_recovery_area).ORACLE has a limitation on this path: it only has 2G of space by default, and it is not only the default path for archive logs, but also the default address for backup files and flash back lo ...
Posted by maheshb on Wed, 08 May 2019 04:35:03 +0200
Hand-in-hand teaching you how to use ORM database gracefully in Flutter project--Part II
A orm database Flutter plugin.
I posted an article earlier. Hand-in-Hand Teaching You Elegant Use of ORM Database in Flutter Project Many people also put forward some valuable suggestions on consulting and using, saying that they do not want to write lua, which is not elegant enough, but also increases the cost of learning. On reflection, it is ...
Posted by hijack on Tue, 07 May 2019 05:00:05 +0200
mybatis input mapping and output mapping
1. parameterType (input type)
(1) Pass simple types (such as int, which we can use directly)
public Student getStudentById(Integer studentId);
<select id="getStudentById" parameterType="int" resultType="student">
select * from tblstudent where studentId = #{studentId}
</select>
(2) Passing pojo objects
p ...
Posted by bogins on Mon, 06 May 2019 22:55:03 +0200
RDD Conversion from Spark-SQL to DataFrame
Case: (bottom)
1. Dynamic programming of metadata to convert RDD into DataFrame - > RDD2 Data Frame Programmatically
2. Reflect RDD-> DataFrame-> RDD2 DataFrame by Reflecting
After RDD is converted to DataFrame, we can use Spark SQL to query any data that can be built into RDD, such as HDFS. This function is extre ...
Posted by webdata on Mon, 06 May 2019 13:45:04 +0200
PostgreSQL Heap Only Tuple - HOT (Reducing Index Writing IO Enlargement Introduced by UPDATE)
Label
PostgreSQL , Heap Only Tuple , HOT
background
PostgreSQL's current default storage engine generates a new version in the heap when updating records. The old version needs to recycle all index POINT associated with this version before it needs to recycle the old version after VACUUM is used.
The KEY of the index of PG is the value of th ...
Posted by Goins on Mon, 06 May 2019 12:45:03 +0200
When configuring relational mapping in 3.2, the table names are different from those in 3.1.
Chapter 3.2 describes the mapping relationship of the corresponding classes according to the steps in the book. It is found that at startup, all the tables previously built in Chapter 3.1 were deleted and re-established, and the data of Ingredient table was lost. Because of the use of JPA, hibernate was used by default, all tables were deleted ...
Posted by axiom82 on Mon, 06 May 2019 04:50:03 +0200
PHP Full Stack Learning Notes 19
image.png
The thinkphp framework is a free, open source, fast and simple object-oriented lightweight PHP development framework.
Learn what is ThinkPHP overview, the directory structure of ThinkPHP projects, the controller of thinkphp, views, the process of building ThinkPHP projects, the configuration of thinkphp, the model o ...
Posted by betazoid on Mon, 06 May 2019 02:50:03 +0200