MyBatis多表关系查询

刺骨的言语ヽ痛彻心扉 2024-04-18 22:02 70阅读 0赞

## ##

### 一、一对一和多对一 ###

图书表

public class Book {
    	private Integer bid;
    	private String bname;
    	private String bauthor;
    	private Double price;
    	private String bdate;
        //图书类型
        private BookType bookType;

图书类型表

public class BookType {
    	private Integer tid;
    	private String name;
    	private Integer pid;

conf.xml添加配置

<typeAliases>
    		<typeAlias type="com.buba.pojo.Book" alias="book"/>
    		<typeAlias type="com.buba.pojo.BookType" alias="bookType"/>
    	</typeAliases>

<association>表关联查询

<resultMap type="book" id="bookMap">
    		<id property="bid" column="bid"/>
    		<result property="bname" column="bname"/>
    		<result property="bauthor" column="bauthor"/>
    		<result property="price" column="price"/>
    		<result property="bdate" column="bdate"/>
    
    		<association property="bookType" javaType="bookType">
    			<id property="tid" column="tid"/>
    			<result property="name" column="name"/>
    			<result property="pid" column="pid"/>
    		</association>
    	</resultMap>
    
    <select id="getBook" parameterType="int" resultMap="bookMap">
    		select * from t_book b,t_type t where b.tid=t.tid and bid=#{id} 
    </select>

### 二、一对多 ###

图书类型表

public class BookType {
    	private Integer tid;
    	private String name;
    	private Integer pid;
    	private List<Book> books;

<collection>配置一对多

<select id="selectBookTypeById" resultMap="bookTypeMap" parameterType="int">
    		select * from t_type t,t_book b where t.tid=b.tid and t.tid=#{id}
    	</select>
    	
    	<resultMap type="bookType" id="bookTypeMap">
    		<id property="tid" column="tid"/>
    		<result property="name" column="name"/>
    		<result property="pid" column="pid"/>
    		<collection property="books" ofType="book">
    			<id property="bid" column="bid"/>
    			<result property="bname" column="bname"/>
    			<result property="bauthor" column="bauthor"/>
    			<result property="price" column="price"/>
    			<result property="bdate" column="bdate"/>
    		</collection>
    	</resultMap>

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