http://www.shangxueba.com/jingyan/122163.html primary key:1. PRIMARY KEY constraint: A table can have only one primary KEY constraint. The primary key can be a single field, or it can be multiple fields. In either case, all of its fields are not NULL.2.Unique constraints: A table can have multiple unique constraints, a
Do you know the key points of the car rental system ?, Key points of the vehicle rental system
Vehicle rental system
The main interface is as follows:
Key Aspect 1: How to clarify the relationships between classes?
Four classes are required: Car class, Truck class, Vehicle class, And VehicleUtil class.
Car: small cars mainly include the calculation method of Ca
For example, the commodity table and the attribute table, because it is many-to-many relationship, so there is a commodity attribute intermediate table;
CREATE TABLE IF not EXISTS
dslxs_goods_attr(
goods_idMediumint (8) unsigned not NULL COMMENT ' Product ID ',
attr_idMediumint (8) unsigned not NULL COMMENT ' property id ',
KEY
goods_id(
goods_id),
KEY
attr_id(
attr_id)
Engine=innodb DEFAULT Charset=utf8
Rimary key database PRIMARY KEY constraint
Database PRIMARY KEY constraintThe PRIMARY KEY constraint uniquely identifies each record in a database table.
The primary key must contain unique values.
Primary key columns cannot co
Tags: allow span to add strict nod keep data repeating mysq data1, definition: If one table has one field pointing to the primary key of another table, the primary key field in the child table is called the foreign key. Multiple foreign keys can exist in a single table2, the role of foreign keys Maintain consistency and integrity of dataA, the role of the chil
Label:Primary key a database primary key is a combination of one column or column in a table whose value uniquely identifies each row in the table. Such a column or columns is called the table's primary key, which enforces the entity integrity of the table. When you create or change a table, you can Create a primary key
Label:Primary key a database primary key is a combination of one column or column in a table whose value uniquely identifies each row in the table. Such a column or columns is called the table's primary key, which enforces the entity integrity of the table. When you create or change a table, you can Create a primary key
Obtain the Baidu map key and map key
Today, when I opened my website, this problem occurs: "Baidu is not authorized to use the map API, it may be because the key you provided is not a valid Baidu Open Platform key or this key is not authorized to the Baidu map JavasoriptAPI
For the extraction of public key private key, see http://www.cnblogs.com/dreamer-One/p/5621134.html for detailsAdditional online encryption and decryption tool Links: Http://tool.chacuo.net/cryptrsaprikey--Public keyLocal Rsa_public_key=[[-----BEGIN RSA Public KEY-----migjaogbaj9yqfctlhnmtyncezmfy7yb7xwazrinxup1zl51517rhjq8w0wvwnt+Mckwrzisa1siqpglhiydb2rjkc1ccnrv
Description: Mycat self-growing primary key and returns the implementation of the generated primary key ID1) MySQL itself on the non-self-growing primary key, using last_insert_id () will not return the result, will only return 0; here's a simple test.
Create a test table
----------------------------------------Create a test table--------------
Summary
When deleting data in a table with a parent-child relationship, we all know that you must delete the child table before deleting the data in the parent table.
Yesterday we used to delete the child table first, then delete the parent table, delete the use of truncate, the results in the deletion of the parent table, given the prompt: ORA-02266 this error message.
When the data in the parent table is deleted using the delete statement, the operation is successful.
The fundament
At the time of the reptile analysis, the RSA public key in the following format is often seen on the Web page:migfma0gcsqgsib3dqebaquaa4gnadcbiqkbgqdc7kw8r6tq43pwapyvkj5laljan9bzb21taift/ Vexbobzh7q8sudp5udpxebkzojx2l28y7xs1d9v3tdpfki2lr7pazwbmdmn8rihrddnpupjnlaguqjg9oopn8j7ynpcxca1iybolc2kehmjn5uwoanqq +ca6agnkqly2h4j6widaqabFor the RSA algorithm's public key, we learned that there are two main information
Tags: success image get class GES new REM technology share creationFor a more secure and convenient login to the Linux server, you can log in using the private key, which is more convenient and more secure.Generate keyWith Xshell you can easily generate and manage private keys, click on the Tools menu and choose the New User Key Generation Wizard:Click Next directlyEnter a name and password, then click Next
The code is as follows
Copy Code
Disable right key, text selection, copy key$ (document). Bind ("ContextMenu", function () {return false;});$ (document). Bind ("Selectstart", function () {return false;});$ (document). KeyDown (function () {return key (Arguments[0])});Prompt warning when pressingFunction key
Tags: htm string triggers display interpreting ref DBA more alterORACLE: Enquiry ( See ) table primary key, FOREIGN key, uniqueness constraint, and index 1. Find all indexes of the table (including index name, type, constituent column)Select T.*,i.index_type from User_ind_columns t,user_indexes i where t.index_name = i.index_name and t.table_name = I.tabl E_name and t.table_name = table name 2. lookup table
Set Expiration
By default, the key is no time to live, that is, never expires, unless the memory is emptied. The key set has a very easy time to live, too 4 Span style= "font-size:14px;font-family: ' The song Body '; > command set (optional): expire pexpire, expireat pexpireat command, this 4 expire and pexpireSet in seconds, set AAA This key expire
Label:1: What is a primary keyIn a table, the set of fields used to uniquely identify a record is called the primary key or primary key, or the primary key (or main code), which says "field set" because the primary key may be represented by a field or multiple fields. For example: Student Table (School number, name, ge
Idea shortcut key, idea shortcut keyIdea shortcut keys
Alt + press enter to import the package, automatically corrected
Ctrl + N lookup class
Ctrl + Shift + N search for files
Ctrl + Alt + L format the code
Ctrl + Alt + O optimized imported classes and packages
Alt + Insert generate code (such as get, set method, constructor, etc)
Ctrl + E or Alt + Shift + C recently changed code
Ctrl + R replace text
Ctrl + F search for text
Ctrl + Shift + Space aut
MyBatis inserts data in batches and returns the primary key. mybatis returns the primary key.
Many people on the Internet say that MyBatis does not support batch insertion and the primary key is returned. This is a misunderstanding. If you want MyBatis to directly return a list containing the primary key, that is, the
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