MongoDB

MongoDB Learning Notes 02–curd operationsCurd represents create (create), update, read (read), and delete operationsCreate a libraryYou can create a library by directly use the library name and then create collectionCreate

MongoDB OverviewMongoDB is a document-type NoSQL database that stores bson–> JSON binaries. The internal execution engine is the JS interpreter, which stores the document as a Bson structure and translates it into a JS object when queried. And can

building an index is a problem that can cause long-time write locks, MongoDB when indexing at the foreground requires a write lock (and does not give up temporarily), if the collection has a large amount of data, it usually takes a long time to

Mybatis one-to-one and one-to-multiple configurationsProblem description There are currently three data tables named orders, orderdetail, and items, indicating orders, order details, and commodities respectively. One order contains multiple order

EF and LINQ call stored procedures I haven't updated my article for a long time. Recently, my project is busy and I have no time to share my recent questions. Today, I encountered a very stupid problem. In C #, the stored procedure is called and its

MongoDB: gradually becoming irrelevantAbstract:Compared with TokuMX and PostgreSQL, MongoDB is at a disadvantage. However, it is still a good product and will continue to improve to compete with these alternative products. However, it can only be

The foreign key constraint column is not indexed, resulting in a large number of librarycachepin/librarycachelockThe foreign key constraint column is not indexed, resulting in a large number of library cache pin/library cache locks.Clear the data of

Group functions and group statisticsGrouping Functions Grouping functions commonly used in SQL Count (): Count Max (): calculates the maximum value. Min (): Minimum value Avg (): calculates the average value. Sum (): Sum -- Count the number of

Implement incremental update in HiveAn insurance company has a table that records the customer information, including the customer's id, name, and age (only these fields are listed for demonstration ).Create a Hive table:Create table customer(Id int,

Improvementsto the Hive Optimizer Improvementsto the Hive Optimizer Hive can be automatically optimized, and some optimization cases are improved in Hive 0.11. 1. The JOIN side is suitable for storing in memory and there are new optimization

Hibernate ing Learning (1) Today, this blog will mainly learn about how to map object classes to tables in hibernate. First, let's take a look at "common primary key generation policies"Common primary key generation policies of hibernate In

Analysis of Database Connection Pool (2) In the previous blog, I briefly introduced the connection process and resources consumed by common databases, and briefly discussed the connection pool, in this article, we will mainly look at the use of

Complex query of tables in the database Complex query of tables in the database 1. Connection query 1.0 the basic syntax format of the connection: from TABLE1 join_type TABLE2 [on (join_condition)] [where (query_condition)] TABLE1: Left table TABLE2

Mybatis delayed Loading If you have such a requirement, You need to query all the orders and obtain detailed information about the orders. If all the required data is requested at one time, the overhead on the server and database will be high.

Logfileswitch (checkpointincomplete) problem locating   Snap Id Snap Time Sessions Cursors/Session Begin Snap: 15257

Query the minimum wage information of each department Example: Query the minimum wage information of each departmentJoin subquery Method 1. query the minimum wage of each department select deptno, min(sal) min_sal from emp group by deptno; 2.

Introduction Now that DB2 9 has been released, it is time to update pureXML, one of its latest features.®To test the driver. Therefore, a simulated brokerage business environment is established. This environment has the following features: High

Use PowerDesigner to convert the table structure in Oracle to the physical data model I recently learned about the subtle relationship between PowerDesigner and oracle because of my work needs. I would like to share my summary with my friends. 1.

B + Tree Index In the database, the height of the B + tree is generally 2 ~ Layer 3, that is, for the row record of a key value, it only needs 2 to 3 times of IO at most. The InnoDB Storage engine table is an index organization table, that is, the

Sentinel cluster construction in Redis and Jedis test graphic tutorial [2] In Redis, the establishment of sentinel clusters and the Jedis test graphic tutorial [1] have already written the setup and testing of sentinel clusters in Redis. This