Employeemapper.xml example, learn Shangang teacher's MyBatis course, record the employeemapper.xml, comments in detail

<?xml version= "1.0" encoding= "UTF-8"?>
<! DOCTYPE Mapper
Public "-//mybatis.org//dtd Mapper 3.0//en"
"Http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace= "Com.atguigu.mybatis.dao.EmployeeMapper" >
<!--
NameSpace: namespace, specified as the full class name of the interface
ID: Unique identifier
Resulttype: Return value type
#{id}: Remove the ID value from the passed parameter
This is the method inside the interface, get the data object: Public Employee Getempbyid (Integer ID);

-

<select id= "Getempbyid" resulttype= "Com.atguigu.mybatis.bean.Employee" databaseid= "MySQL" >
Select ID, last_name LastName, email from tbl_employee where id = #{id}
</select>

<select id= "Getempbyid" resulttype= "Com.atguigu.mybatis.bean.Employee" databaseid= "Oracle" >
Select employee_id ID, last_name lastName, GENDER GENDER, email
From EMPLOYEE where employee_id = #{id}
</select>

<select id= "selectemp" resulttype= "Com.atguigu.mybatis.bean.Employee" databaseid= "MySQL" >
Select ID, last_name LastName, email, gender from tbl_employee where id = #{id}
</select>

<!--public void Addemp (employee employee); -
<!--Gets the value of the self-increment primary key:
MySQL supports self-increment primary key, self-increment primary key value obtains, MyBatis also uses Statement.getgeneratedkeys () to obtain
Add usegeneratedkeys= "True" to the insert tag; use the self-increment primary key to get the primary key value policy
Keyproperty: Used to specify the value assigned to the obtained primary key value, which can be encapsulated in the employee.id of JavaBean
-
<!--usegeneratedkeys= "true" keyproperty= "id"--
<insert id= "addemp" databaseid= "MySQL" >
INSERT into Tbl_employee (ID, last_name, gender, email) VALUES (#{id}, #{lastname}, #{gender}, #{email})
</insert>
<!--Oracle does not support self-increment, but Oracle can use sequences to simulate the self-increment
The primary key value of each inserted data is the value obtained from the sequence;
-
<!--keyproperty: An attribute ID that identifies the primary key and encapsulates it to JavaBean
Order = "Before" specifies that the current SQL runs before the insert operation
= "After" is specified after the current SQL
Resulttype: What type of primary key to encapsulate is found, which needs to be specified here
Before run Order: SQL that runs the Selectkey query ID first: id attribute for ID encapsulation to JavaBean is isolated
Run the inserted SQL again to remove the value of the id attribute
After run order: First run the inserted SQL (remove the new value from the sequence as the ID
Run the Selectkey isolated ID again sql-->
<insert id= "addemp" databaseid= "Oracle" >
<!--<selectkey keyproperty= "id" order = "before" >
Select Employee_seq.nextval from dual
</selectKey>
<!--the primary key to insert is taken from the sequence.
<!--before--><!--, Jdbctype=null--
Insert into EMPLOYEE (employee_id, Last_name,gender,email) VALUES (#{id}, #{lastname}, #{gender}, #{email})
</insert>

<!--can also write this--
<!--after--
<!--
<insert id= "addemp" databaseid= "Oracle" >
<selectkey keyproperty= "id" order = "after" >
Select Employee_seq.currval from dual</selectkey>
-
<!--INSERT INTO EMPLOYEE (employee_id, Last_name,gender,email)
VALUES (Employee_seq.nextval, #{lastname}, #{gender}, #{email})--
<!--multi-parameter query--
<select id= "Getempbyidandlastname" resulttype= "Com.atguigu.mybatis.bean.Employee" >
SELECT * from EMPLOYEE where employee_id = #{id} and last_name = #{lastname}
</select>
<!--multi-parameter query, using map to encapsulate parameters--
<select id= "Getempbymap" resulttype= "Com.atguigu.mybatis.bean.Employee" >
SELECT * from EMPLOYEE where employee_id = #{id} and last_name = #{lastname}
</select>
<!--public void deleteemp (Integer id); -
<delete id= "Deleteempbyid" >
Delete from EMPLOYEE where employee_id = #{id}
</delete>

<!--public void Updateemp (employee employee); -
<update id= "Updateemp" >
Update EMPLOYEE
Set last_name = #{lastname}, EMAIL = #{email}, GENDER = #{gender}
WHERE id = #{id}
</update>

</mapper>

Employeemapper.xml example, learn Shangang teacher's MyBatis course, record the employeemapper.xml, comments in detail