Tidy up your study Aaron Saray Write some demo s of PHP design patterns and their own understanding. If you find that your contempt has misunderstood, please point out immediately. Thank you for patting bricks and kneeling for whipping.
* DAO (Data Access Objects) Data Access Objects
* ** From Exp ...
Posted by chigley on Tue, 12 Feb 2019 18:27:19 -0800
Premise: web development, spring+mybatis+mysql, using mybatis to automatically generate plug-ins to automatically generate various classes, mapping documents and so on from database forms.
Symptoms: When the user registration function is implemented, it is found that insert user data is not available. When the controller calls the insert met ...
Posted by marijn on Tue, 12 Feb 2019 17:30:17 -0800
For many Optimzer problems in SQL, such as abnormal execution plan, slow SQL, Wrong Result, etc.
If the test environment can be reproduced, it can be through the xplore function of SQLT.
Adjust various parameters and Optimzer's Fix Control t ...
Posted by afam4eva on Tue, 12 Feb 2019 00:57:18 -0800
PostgreSQL, aggregation, filter, order, within group
PostgreSQL has powerful analysis functions, such as supporting multi-dimensional analysis, supporting four kinds of aggregation, supporting window query, supporting recursive query and so on.
For the use of four major types of aggregation, please refer to
<PostgreSQL ag ...
Posted by thirdeye on Mon, 11 Feb 2019 17:09:19 -0800
1.Maven refers to the jar package
The default mybatis can't print out the SQL log, which is not easy to view and debug. It needs to be combined with log4jdbc-log4j2 to complete the input of the debugging information of SQL.
Configure maven with pom.xml. Note that all three of the following are required
Posted by dmb on Mon, 11 Feb 2019 11:45:19 -0800
1.Sql Server row-column transitions,
select count(*) as TotalCount,SchoolId,Type,
row_number()over(order by Type asc) as RowIds
group by [Type] ,SchoolId
Query through SQL PRIVOT
with temp as (
select count(*) as TotalCount,SchoolId,Type,year(AddDate) as [Year]
group by ...
Posted by badgoat on Mon, 11 Feb 2019 10:21:18 -0800
The reasons for the error are as follows:
Exception in thread "main" org.hibernate.exception.JDBCConnectionException: Cannot open connection
at org.hibernate.exception.JDBCExc ...
Posted by strangebeer on Sun, 10 Feb 2019 18:54:18 -0800
I. Introduction In oracle, start with connect by (prior) is used to query tree-structured data. start with conditon gives the scope of data search. Conneby gives the condition of recursive query. Prior keyword denotes the parent data. Prior condition denotes what condition the child data needs to satisfy the parent data. as follows start with i ...
Posted by MadDogSh on Sun, 10 Feb 2019 08:36:17 -0800
Order by limit x, X has various business needs in the actual work to have order by ordering, sometimes it will cause system downtime if it is not handled properly! ___________
a. Get sorting by index
b. Get ranking by internal algorithm:
SELECT c.order_price orderPrice,
Posted by Buddha443556 on Sun, 10 Feb 2019 05:12:19 -0800
Query the database table and return the object of the data if there is a data whose username is lisi in the user table sw_user
Using the original method, the operation is as follows:
1. Write a tool class first. There are ways to realize MySQL database connection, and methods to close database connection, ResultSet result set and PreparedStatem ...
Posted by jkm4201 on Sat, 09 Feb 2019 22:21:20 -0800