描述：有三張表，商家登入表，商家表，商家資料資訊表。商家登入後，通過商家id去查詢商家表資訊，然後通過商家表id去查詢商家資料表資訊，登入成功後需儲存三張表資訊到session中。這其中需要用到聯合查詢。

1.Mapper

<span style="font-family:Microsoft YaHei;"><select id="selectAccountInfors" parameterType="java.lang.String" resultType="map">
  select  
  sm.id as sm_id, `name`,......,
  smi.id as smi_id, ......, mark<span style="white-space:pre">								</span>
  from seller_merchant as sm <span style="white-space:pre">		</span>//聯合查詢第二張和第三張表
  inner join seller_merchant_info as smi on smi.merchantId = sm.id
  where sm.accountId=#{accountid}
  </select></span>
 

<span style="font-family:Microsoft YaHei;">/**
	 * 查詢登入商家的商戶表和商戶資料表資訊
	 * @param accountid
	 * @return
	 */
	<strong><span style="color:#ff0000;">public List<Map<String,Object>> selectAccountInfors(String accountid);</span></strong></span>
 

<span style="font-family:Microsoft YaHei;">public boolean queryMerchant(SellerMerchantAccount merchant,HttpSession session) {
		CriteriaParameter cp = new CriteriaParameter();
		Criteria cri = cp.createCriteria();
		cri.equalTo("account", merchant.getAccount());
		cri.equalTo("state", 0);
		//判斷是否有該使用者，且該使用者的狀態必須是可用狀態
		List<SellerMerchantAccount> account = accountMapper.selectByExample(cp);
		if(!account.isEmpty()){
			cri.equalTo("password", merchant.getPassword());
			//判斷使用者名稱，密碼，狀態
			List<SellerMerchantAccount> acc = accountMapper.selectByExample(cp);
			if(!acc.isEmpty()){
				//根據使用者賬號id獲取商家表資訊
				String accountid = null;
				for (SellerMerchantAccount sellerMerchantAccount : acc) {
					accountid = sellerMerchantAccount.getId();
				}				
				MerchantInformation information = new MerchantInformation();
				information.setId(accountid);
				information.setAccount(merchant.getAccount());
				information.setLoginTime(BaseUtil.timeToString(new Date()));
				<strong><span style="color:#ff0000;">List<Map<String,Object>> l = accountMapper.</span></strong><span style="color:#ff0000;"><strong>selectAccountInfors</strong></span><strong><span style="color:#ff0000;">(accountid)</span></strong>;
				for (Map<String, Object> map : l) {
					information.setLoginAccountInfors(map);
				}
				//將使用者的賬號id，賬號，登入時間，商戶表，商戶資料資訊表儲存到session中
				session.setAttribute("MERCHANT_LOGIN-INFOR",information);
				return true;
			}
			
		}
		return false;
	}</span>
 

<span style="font-family:Microsoft YaHei;">/**
	 * 商戶登入
	 * @param account
	 * @return
	 */
	@RequestMapping(value="/loginMerchant",method=RequestMethod.POST)
	public ResultData loginMerchant(SellerMerchantAccount account,HttpSession session){
		try {
			return new ResultData(merchantService.queryMerchant(account, session));
		} catch (Exception e) {
			e.printStackTrace();
			return SchExceptionUtil.ExceptionConvertState(e);
		}
	}</span>

<span style="font-family:Microsoft YaHei;">/**
	 * 商戶賬戶id
	 */
	private String id ;
	
	/**
	 * 商戶賬戶
	 */
	private String account;
	
	/**
	 * 商戶登入時間
	 */
	private String loginTime;
	
	/**
	 * 商戶表和商戶資料表
	 */
	<span style="color:#ff0000;"><strong>private Map<String,Object> loginAccountInfors;//用來儲存聯合查詢的結果</strong></span></span>