使用Mybatis进行连表查询、left join
目前有个需求：
条件筛选出一个A表的结果list，然后需要增加一个字段，另一张B表的uuid，
他们之间的关联关系是 a.uuid=b.releaseUuid,
若不存在则返回null.
因此考虑用左连接,不存在字段也不影响总的A表条数
本来实体
dao:
/**
* t_table dao
* @author Mingchenchen
*
*/
public interface ReleaseDao{
/**
* 获取条件筛选结果的总数
* @param parameterMap
* @return
*/
public Integer getCountByCondition(Map parameterMap);
/**
* 列表 条件筛选
* @param releaseEntity
* @return
*/
public List getReleaseListByCondition(Map parameterMap);
}
Entity:
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Id;
import javax.persistence.Table;
/**
* 实体
* @author Mingchenchen
*
*/
@Table(name = "t_table")
public class ReleaseEntity {
@Id
private String uuid;
@Column
private String name;
@Column(name = "app_name")
private String appName;
@Column(name = "app_uuid")
private String appUuid;
@Column(name="deploy_type")
private String deployType;//
@Column(name="department_code")
private String departmentCode;//
@Column(name="department_name")
private String departmentName;//
@Column(name = "status")
private int status;//状态 0:已创建 1:已编排 2:已部署
@Column(name = "flag")
private int releaseType;//
@Column(name="delete_flag")
private int deleteFlag;//
@Column(name = "create_time")
private Date createTime;
@Column(name = "create_user")
private String createUser;
@Column(name = "update_time")
private Date updateTime;
@Column(name = "update_user")
private String updateUser;
@Column(name = "remark")
private String remark;
/** 多余返还的字段 不要注解column 否则insert会报错 相当于让mybatis忽略此字段 */
private String departmentCode;//所属业务线的简码
private String departmentName;//所属业务线的名称
private String deployType;//发布单的部署类型:QA TEST DEV PRODUCT
private String namespace;
/*
* Getter and setter
*/
}Mybatis xml sql:
<mapper namespace="com.xxx.dao.ReleaseDao">
<resultMap id="microServiceResultMap" type="MicroServiceEntity">
<id property="uuid" column="uuid" />
<result property="name" column="name" />
<result property="version" column="version" />
<result property="ports" column="port_metadata" />
resultMap>
<resultMap id="releaseResultMap" type="ReleaseEntity">
<id property="uuid" column="uuid" />
<result property="name" column="name"/>
<result property="appName" column="app_name"/>
<result property="appUuid" column="app_uuid"/>
<result property="deployType" column="deploy_type"/>
<result property="departmentCode" column="department_code"/>
<result property="departmentName" column="department_name"/>
<result property="status" column="status"/>
<result property="qps" column="qps"/>
<result property="releaseType" column="dms_flag"/>
<result property="deleteFlag" column="delete_flag"/>
<result property="createTime" column="create_time"/>
<result property="createUser" column="create_user"/>
<result property="updateTime" column="update_time"/>
<result property="updateUser" column="update_user"/>
<result property="remark" column="remark"/>
<result property="layoutTemplateUuid" column="layout_template_uuid"/>//第二张表的字段
resultMap>
<select id="getCountByCondition" parameterType="java.util.Map" resultType="java.lang.Integer">
select count(*)
from dms_release
where 1=1
<if test="releaseStatu != null and releaseStatu != -1">
and status = #{releaseStatu}
if>
<if test="appName != null and appName !=''">
and app_name like #{appName}
if>
<if test="deployType != null and deployType != ''">
and deploy_type = #{deployType}
if>
<if test="departmentCode != null and departmentCode != ''">
and department_code = #{departmentCode}
if>
and delete_flag = 0
select>
<select id="getReleaseListByCondition" parameterType="java.util.Map"
resultMap="releaseResultMap">
SELECT
d.department_code,d.department_name,
d.status,d.qps,d.dms_flag,d.delete_flag,d.create_time,
d.create_user,d.update_time,d.update_user,
d.remark,
l.uuid as layout_template_uuid //需要第二张表的uuid
FROM
d_table as d
LEFT JOIN l_table as l
ON d.uuid=l.release_uuid
AND l.delete_flag=0 //注意此处join的那张表的查询条件必须写在ON后不能写在最后面
WHERE 1=1
<if test="releaseStatu != null and releaseStatu != -1">
and d.status = #{releaseStatu}
if>
<if test="appName != null and appName !=''">
and d.app_name like #{appName}
if>
<if test="deployType != null and deployType != ''">
and d.deploy_type = #{deployType}
if>
<if test="departmentCode != null and departmentCode != ''">
and d.department_code = #{departmentCode}
if>
AND d.delete_flag = 0
ORDER BY d.create_time
DESC LIMIT #{pn},#{ps}
//pn是开始下表 从0开始
//ps是总条数 比如是10,10 即从10条开始,共需10条 ,而不是10,20
select>
mapper>优化
before:
SELECT
a.name,a.uuid,a.app_name,a.app_uuid,a.release_uuid,a.release_name,
a.layout_template_name,a.layout_template_uuid,a.layout_template_version,
a.cluster_uuid,a.status,a.remark,a.delete_flag,
a.create_time,a.create_user,a.update_time,a.update_user,
d.department_code,d.deploy_type,d.department_name,d.namespace
FROM app_instance as a
LEFT JOIN dms_release as d
ON a.release_uuid = d.uuid
AND d.delete_flag=0
WHERE a.delete_flag=0
ORDER BY a.create_time
DESC LIMIT 1,2after：
SELECT
a.name,a.uuid,a.app_name,a.app_uuid,a.release_uuid,a.release_name,
a.layout_template_name,a.layout_template_uuid,a.layout_template_version,
a.cluster_uuid,a.status,a.remark,a.delete_flag,
a.create_time,a.create_user,a.update_time,a.update_user,
d.department_code,d.deploy_type,d.department_name,d.namespace
FROM (
select * from app_instance where delete_flag=0
ORDER BY create_time desc LIMIT 1,2
) as a
LEFT JOIN dms_release as d
ON a.release_uuid = d.uuid
AND d.delete_flag=0
ALTER TABLE app_instance ADD INDEX index_release_uuid (release_uuid)思路:
1.先筛选出符合条件的再进行join,而不是先全表join再筛选
2.加入关键选项的索引