Chapter 2 build CRM project development environment (database design)

2.1CRM Database design

2.1.1 Database design principles

We can consider the database design in combination with the project prototype , Marketing activities , user , These need to be persistent , So it needs to be designed as a table . There is usually a certain relationship between tables . Look at the attributes on each creation form .

1、 All tables come from requirements ：

    Noun , Especially business-related terms . Clarify the relationship between nouns .

    Conceptual nouns are designed into tables 、 Descriptive nouns are designed as fields .

    Some obscure nouns , Need to be abstract , Such as data dictionary table and data dictionary type table

2、 Field ：

       1> Primary key : There are many fields in the table , If a group of fields can uniquely identify a record , You can design this group of fields as primary keys . In general , A field is used as the primary key , And fields without business semantics are used as primary keys . Of course , In some cases, business-related fields are used as primary keys .

      How to generate primary key ： Determine the type of the primary key field and the length of the primary key field .

a、 Self increasing ： Adopt the primary key generation mechanism provided by database .

         Mysql:auto_increment

         Oracle:sequence

        Due to the common database , Such as Oracle、DB2、SQLServer、MySql etc. , They all provide an easy-to-use primary key generation mechanism （Auto-Increase Field or Sequence）. We can use the primary key generation mechanism provided by the database , use generator-class=native How to generate primary key .
        But here's the thing , The primary key generation mechanism provided by some databases may not be the best in efficiency , Massive concurrency insert Data synchronization may cause interlocking between tables .
         Primary key generation mechanism provided by database , Often by saving the current primary key state in an internal table （ For example, for a self increasing primary key , The current maximum value and increment are maintained in this internal table ）, After that, the maximum value will be read every time the data is inserted , Then add the increment as the primary key of the new record , Then update the new maximum value back to the internal table , such , once Insert Operation may cause multiple table read and write operations inside the database , At the same time, it is accompanied by data locking and unlocking operation , This has a big impact on performance . therefore , For concurrency Insert A more demanding system , Recommend uuid.hex As a primary key generation mechanism .

b、assigned： External programmers are responsible for generating .

UUID,

hi/lo,

Twitter-Snowflake The background of the algorithm is quite simple , In order to satisfy the Twitter Requests for tens of thousands of messages per second , Each message must be assigned a unique id, these id We need some general order （ Convenient for client sorting ）, And in a distributed system, different machines produce id Must be different .

c、 Shared primary key ：

d、 Combined the primary key ：

     2>、 Foreign keys ： Foreign keys are used to represent the relationship between tables . Some run without foreign keys , Is to ensure the integrity of data through procedures .

     3>、 Use of date data char type

 

1,crm The table structure ：
  tbl_user   User table

  tbl_dic_type   Data dictionary type table
  tbl_dic_value  Data dictionary values

  tbl_activity   Market activity table
  tbl_activity_remark  Notes to market activities

  tbl_clue       Clue table
  tbl_clue_remark   Clue remarks table

  tbl_clue_activity_relation  Table of the relationship between clues and market activities

  tbl_customer   Customer list
  tbl_customer_remark  Customer remarks table

  tbl_contacts   Contact list
  tbl_contacts_remark Contact notes table

  tbl_contacts_activity_relation Table of the relationship between contacts and marketing activities

  tbl_tran       Deal sheet
  tbl_tran_remark  Transaction notes table
  tbl_tran_history  Transaction history table

  tbl_task   Task list

  1) Primary key field ： In the database table , If a group of fields can uniquely identify a record , You can design them as the primary key fields of the table .
              It is recommended to use a field as the primary key , And it is recommended to use fields without business meaning as primary keys , such as ：id etc. .

          The type and length of the primary key field are determined by the generation method of the primary key value ：
                   How to generate primary key values ：
               1) Self increasing ： With the help of the database's own primary key generation mechanism
                       Numerical type The length is determined by the amount of data

                   Low operating efficiency
                   High development efficiency
               2)assighed： Programmers manually generate primary key values , The only one is not empty , Algorithm .
                       hi/low： Numerical type The length depends on the amount of data
                   UUID： character string The length is 32 position
               3) Shared primary key ： Determined by the type and length of another table
                       tbl_person         tbl_card
                   id     name        id     name
                   1001   zs          1001    card1
                   1002   ls
               4) Combined the primary key ： Determined by the type and length of multiple fields
   2) Foreign key field ： Used to determine the relationship between tables .
              1) One to many ： A watch (A) A record in can correspond to another table (B) Multiple records in ;
                    The other table (B) A record in can only correspond to one table (A) One of the records .
            A(1)---------B(n)
             Parent table          Sub table
            tbl_student                    tbl_class
            id      name class_id          id     name
            1001    zs    111              111    class1
            1002    ls    111              222    class2
            1003    ww    222
            1004    zl    

             When adding data , First add the parent table record , Add sub table records ;
             When deleting data , Delete the sub table record first , Then delete the parent table record ;
             When querying data , Association query may be performed ：
            // Check the names of all students surnamed Zhang id,name And your class name
            select s.id,s.name,c.name as className
            from tbl_student s
            join tbl_class c on s.class_id=c.id// If the foreign key cannot be empty
            where s.name like 'z%'

             Internal connection ： Query all qualified data , And the results are required to have corresponding records in both tables
             The left outer join ： Query all qualified data in the table on the left , Even if there is no corresponding record in the table on the right
                     
                * If the foreign key cannot be empty , Internal connections are preferred ;
             If the foreign key can be empty ,
                               -- Suppose you only need to query those records that have corresponding records in another table , Use internal connections
                       -- If you need to query all the qualified records in the table on the left , Use left outer connection .
        2) one-on-one ： A watch (A) A record in can only correspond to another table (B) One of the records ;
                  The other table (B) A record in can only correspond to one table (A) One of the records .
            tbl_person         tbl_card
            id     name        id     name
            1001   zs          1001    card1
               a) Shared primary key ：( Not recommended )
                 Add data ： First add the generated table , The table records generated later
             Delete data ： Table records generated after deletion , Then delete the table record generated first
             Query data ： No connection query is required
                       // Inquire about zhangsan Driver's license information   1001
                   select *
                   from tbl_card
                   where id='1001'
                       b) The only foreign key ：
                 tbl_person             tbl_card
             id     name            id     name     person_id( Uniqueness constraint )
             1001   zs              111    card1    1001
             1002   ls              222    card2    1002
             1003   ww              333    card3    1003
             * One to one is a special one to many .
             * The operation is exactly the same as one to many .
         3) Many to many ： A watch (A) A record in can correspond to another table (B) Multiple records in ;
                   The other table (B) A record in can also correspond to a table (A) Multiple records in .
               tbl_student                    tbl_course
               id     name                    id     name   
               1001   zs                      111    java   
               1002   ls                      222    mysql  
                       tbl_student_course_relation
                    student_id     course_id
                1001            111
                1001            222
                1002            111
                1002            222
               When adding data , First add the parent table record (tbl_student,tbl_course), Add sub table (tbl_student_course_relation) Record ;
               When deleting data , Delete the sub table record first (tbl_student_course_relation), Then delete the parent table record (tbl_student,tbl_course)
               When querying data , Association query may be performed ：
                  // Check the names of all students surnamed Zhang id,name, And the... Of the selected course name
              select s.id,s.name,c.name as courseName
              from tbl_student s
                          join tbl_student_course_relation scr on s.id=scr.student_id
                          join tbl_course c on scr.course_id=c.id
              where s.name like 'z%'
  3) Give fields about date and time ：
     Are handled as strings ：
     char(10)   yyyy-MM-dd
     char(19)   yyyy-MM-dd HH:mm:ss

2, establish crm Database instance of ：
  hold sql Script import database instance ：

3, Build development environment ：
  1) Create project ：crm-project
              Set up JDK.
    Create a project ：crm
              Complete directory structure ：
  2) add to jar package