Mybatis中 SQL语句复用

mapper.xml 中共用

mapper.xml 间共用

项目中也许我们会遇到一段sql语句被多个查询、增加等语句用到的情况，如何去偷懒呢，复用sql无疑是较好的选择

这里只提供简单的示范：

如果只是单表查询，并且希望共用的sql只会出现在同一个mapper.xml文件中，那么我们可以直接在

<mapper namespace="XXXXX"></mapper>

中写下面的业务代码

<sql id="unitSql">
    a.userId,a.legalCode,legalName,
    bidderCodeType,legalRole,
    licenseNo,DATE_FORMAT(licenseEndDate,"%Y-%m-%d") AS licenseEndDate,
    taxCertNo,DATE_FORMAT(taxCertEndDate,"%Y-%m-%d") AS taxCertEndDate,
    localTaxCertNo,DATE_FORMAT(localTaxCertEndDate,"%Y-%m-%d") AS localTaxCertEndDate,
    organNo,DATE_FORMAT(organCertEndDate,"%Y-%m-%d") AS organCertEndDate,
    legalRepresent,legalType,
    perresentPhone,legalIndustary,creditRate,
    countryRegion,legalUnitAddress,regionCode,registerProvince,
    a.regCapital,a.regCapCurRency,a.regUnit,
    registerCity,registerCounty,basicBank,basicBranchBank,
    basicAccountNo,basicAccountName,legalContact,legalContactPhone,
    legalContactAddress,legalWeb,legalZipCode,legalEmail,
    legalStatus
</sql>

然后引用

<select id="getTenderAgentById" parameterType="String" resultType="Map">
    select <include refid="unitSql"/>, -- 就是这句话引用 ，refid为共有sql语句id
    b.auditOpinion,b.createUser,
    b.createTime,
    b.lastUpdateUser,
    b.lastUpdateTime,
    b.disabled,b.infoStatus
    from P_legalUnit a, P_tenderAgent b
    where b.userId=#{userId} AND a.userId = b.userId AND b.disabled='0'
</select>

如果是连表查询，那么我们极有可能会希望有一个sql语句被多个mapper.xml引用的的方法，很简单。
我们可以新建一个mapper.xml文件（当然，这个mapper.xml要在你的扫描路径下，本文不赘述）。取名为common.xml

该文件内容为

<?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="common">
  <sql id="common.unitSql">
    a.userId,a.legalCode,legalName,
    bidderCodeType,legalRole,
    licenseNo,DATE_FORMAT(licenseEndDate,"%Y-%m-%d") AS licenseEndDate,
    taxCertNo,DATE_FORMAT(taxCertEndDate,"%Y-%m-%d") AS taxCertEndDate,
    localTaxCertNo,DATE_FORMAT(localTaxCertEndDate,"%Y-%m-%d") AS localTaxCertEndDate,
    organNo,DATE_FORMAT(organCertEndDate,"%Y-%m-%d") AS organCertEndDate,
    legalRepresent,legalType,
    perresentPhone,legalIndustary,creditRate,
    countryRegion,legalUnitAddress,regionCode,registerProvince,
    a.regCapital,a.regCapCurRency,a.regUnit,
    registerCity,registerCounty,basicBank,basicBranchBank,
    basicAccountNo,basicAccountName,legalContact,legalContactPhone,
    legalContactAddress,legalWeb,legalZipCode,legalEmail,
    legalStatus
  </sql>
</mappper>

在另一个mapper.xml文件引用

<select id="getTenderAgentById" parameterType="String" resultType="Map">
    select <include refid="common.unitSql"/>, -- 就是这句话引用 ，refid为共有sql语句id
    b.auditOpinion,b.createUser,
    b.createTime,
    b.lastUpdateUser,
    b.lastUpdateTime,
    b.disabled,b.infoStatus
    from P_legalUnit a, P_tenderAgent b
    where b.userId=#{userId} AND a.userId = b.userId AND b.disabled='0'
</select>

==注:为何我的文件名要取为common.xml并且id也为common.unitSql呢？这是为了后期维护方便，如此，可以更容易找到该共有的sql在哪一个文件==

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