Mybatis进阶学习笔记——动态sql

1.if标签

    <select id="queryByNameAndTelephone" parameterType="Customer"
        resultType="Customer">
        SELECT * FROM t_customer
        WHERE 1=1
        <if test="name!=null and name!=''">
            AND NAME LIKE #{name}
        </if>
        <if test="telephone!=null and telephone!=''">
            AND telephone LIKE #{telephone}
        </if>
    </select>

 public List<Customer> queryByNameAndTelephone(Customer customer); 

    /**
     * if标签使用
     */
    @Test
    public void test1() {
        SqlSession sqlSession = SessionUtils.getSession();
        // getMapper(): 返回指定接口的动态代理的实现类对象
        CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
        Customer c = new Customer();
        //c.setName("%陈%");
        c.setTelephone("%55%");
        List<Customer> list = dao.queryByNameAndTelephone(c);
        for (Customer customer : list) {
            System.out.println(customer);
        }
        sqlSession.commit();
        sqlSession.close();
    }

2.where标签：自动把第一个条件的and去掉

    <select id="queryByNameAndTelephone" parameterType="Customer"
        resultType="Customer">
        SELECT * FROM t_customer
        <!-- <where>：where条件，自动把第一个条件的and去掉 -->
        <where>
            <if test="name!=null and name!=''">
                AND NAME LIKE #{name}
            </if>
            <if test="telephone!=null and telephone!=''">
                AND telephone LIKE #{telephone}
            </if>
        </where>
    </select>

3.sql片段

作用：把相同的sql片段抽取出来

    <!-- sql片段 -->
    <sql id="customerField">
        id,name,gender,telephone
    </sql>

    <select id="queryByNameAndTelephone" parameterType="Customer"
        resultType="Customer">
        SELECT
        <include refid="customerField"/>
        FROM t_customer
        <!-- <where>：where条件，自动把第一个条件的and去掉 -->
        <where>
            <if test="name!=null and name!=''">
                AND NAME LIKE #{name}
            </if>
            <if test="telephone!=null and telephone!=''">
                AND telephone LIKE #{telephone}
            </if>
        </where>
    </select>

4.foreach标签

    <delete id="deleteCustomerByIn" parameterType="Customer">
        DELETE FROM t_customer WHERE 
        <!-- 
            collection: 需要遍历的属性
            item: 遍历的变量
            open: 循环前面的 sql语句
            close： 循环后面的 sql语句
            separator：分隔符
            
            id IN(1,2,3)
         -->
         <!-- id为ids数组中的每个元素 -->
        <foreach collection="ids" item="id" open="id IN (" close=")" separator=",">
            #{id}
        </foreach>
    </delete>

 public void deleteCustomerByIn(Customer customer); 

    /**
     * foreach标签
     */
    @Test
    public void test2() {
        SqlSession sqlSession = SessionUtils.getSession();
        // getMapper(): 返回指定接口的动态代理的实现类对象
        CustomerDao dao = sqlSession.getMapper(CustomerDao.class);
        Customer c = new Customer();
        Integer[] ids = {23,24,25};
        c.setIds(ids);
        dao.deleteCustomerByIn(c);
        sqlSession.commit();
        sqlSession.close();
    }

Customer.java：

package cn.sm1234.domain;

import java.util.Arrays;

public class Customer {

    private Integer id;
    private String name;
    private String gender;
    private String telephone;
    
    private Integer ids[];
    
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    public String getTelephone() {
        return telephone;
    }
    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }
    public Integer[] getIds() {
        return ids;
    }
    public void setIds(Integer[] ids) {
        this.ids = ids;
    }
    @Override
    public String toString() {
        return "Customer [id=" + id + ", name=" + name + ", gender=" + gender + ", telephone=" + telephone + ", ids="
                + Arrays.toString(ids) + "]";
    }
    
    
}